Stud Calculator
The studs in a wall from its length and on-center spacing, rounded up once, with your own corner and opening counts, the plates, the lumber list and, at your own price, the cost.
The working
Wall length in inches = Wall length × 12
= 20 ft × 12
= 240 in
Spaces = Wall length ÷ Spacing
= 240 in ÷ 16 in
= 15 spaces
Layout studs = Spaces (rounded up) + 1
= 15 + 1
= 16 studs
Other spacings, 12 in: Spaces = Wall length ÷ Spacing
= 240 in ÷ 12 in
= 20 spaces
Other spacings, 12 in: Layout studs = Spaces (rounded up) + 1
= 20 + 1
= 21 studs
Studs
studs
Layout studs only: no corner, intersection or opening studs entered.
- Layout studs
- 16studs
Which code and edition apply, and any local amendment, are decided by your jurisdiction. This page does not say whether a wall meets a code. The ICC states that the IRC is in use or adopted in 49 states, the District of Columbia, Guam, Puerto Rico and the U.S. Virgin Islands, and that some jurisdictions amend the code in the process. The figures quoted from the 2024 IRC and the 2024 WFCM are in a table with the results, each beside your own number.
Layout studs for this wall at other spacings
| Spacing on center | Spaces, length ÷ spacing | Layout studs, rounded up + 1 |
|---|---|---|
| 12 in | 20 | 21 |
| 16 in (yours) | 15 | 16 |
| 19.2 in | 12.5 | 14 |
| 24 in | 10 | 11 |
Figures quoted from the model code and AWC, beside your own
| Item | Quoted | Your wall |
|---|---|---|
| Stud spacing, 2 × 4 | Table R602.3(5), 2 × 4 studs, bearing walls, 10 ft laterally unsupported height: maximum spacing 24 in where supporting a roof-ceiling assembly or a habitable attic assembly only, 16 in where supporting one floor plus a roof-ceiling or habitable attic assembly (footnote c on both), none tabulated for two floors. Nonbearing walls, 14 ft: 24 in. The table’s other columns and footnotes apply too. | 16 in on center |
| Stud spacing, 2 × 6 | Table R602.3(5), 2 × 6 studs, bearing walls, 10 ft: 24 in for a roof-ceiling or habitable attic assembly only, 24 in for one floor plus a roof-ceiling assembly, 16 in for two floors plus a roof-ceiling assembly. Nonbearing walls, 20 ft: 24 in. | 16 in on center |
| Top plate | R602.3.2: “Wood stud walls shall be capped with a double top plate installed to provide overlapping at corners and intersections with bearing partitions. End joints in top plates shall be offset not less than 24 inches (610 mm).” Its exception allows a single top plate in place of the double one on these conditions: it is tied at corners, intersecting walls and in-line splices as Table R602.3.2 sets out, and the rafters or joists are centered over the studs within 1 inch (25 mm); the exception also lets the top plate be omitted over headers that are adequately tied to the adjacent wall sections as that table sets out. WFCM 3.4.1.2: double top plates on exterior stud walls, overlapping at corners; 3.4.3.2: “Single or double top plates” on interior nonloadbearing partitions. | no top plate courses entered |
| Bottom plate | R602.3.4: studs “shall have full bearing on a nominal 2-by (51 mm) or larger plate or sill having a width not less than to the width of the studs.” | no bottom plate courses entered |
| Corners | WFCM 3.4.1.1.3: “A minimum of three studs shall be provided at each corner of an exterior wall”, with an exception where shear walls are not continuous to corners. | no corner studs entered; no intersection studs entered |
| Header supports | R602.7.5: headers are supported at each end “with one or more jack studs or with approved framing anchors”; the minimum number of full-height studs at each end follows Table R602.7.5 (exterior walls). For a header span of 4 ft it is 1; for 6 or 8 ft, 2 in the “< 140 mph, Exposure B or < 130 mph, Exposure C” column and 1 in the “≤ 115 mph, Exposure B” column; for 10 to 14 ft, 3 in the first column and 2 in the second; for 16 or 18 ft, 4 in the first column and 2 in the second. The table’s footnotes apply too, among them one for spans between those given and one for a framing anchor used in place of a jack stud. WFCM 3.4.1.4.2 (exterior walls): the minimum number of full-height studs at each end of a header “shall not be less than half the number of studs replaced by the opening”, in accordance with Table 3.23C (by header span and stud spacing, for wind Exposures B and C), and the number may be reduced under Table 3.23D; 3.4.1.4.3: the number of jack studs per Table 3.22F. | no openings entered |
Enter the wall length and the spacing on your plans. The calculator counts a stud at every mark from one end and a closing stud at the far end, rounding the spaces up once, and adds only the extra studs you enter for corners, intersections and openings. It turns the count into pieces by length, plate boards and board feet on the nominal size, and prices it only at prices you enter. Waste is yours and blank. It does not say which spacing or how many studs a wall needs: the sections of the 2024 IRC and the WFCM that speak to that are quoted beside your numbers.
How this calculator works
Only your inputs and exact unit conversions. Where a figure comes from anywhere else, it is recorded below with its source.
- Formula version
- 1.0.0
- Last reviewed
- 2026-09-30
- External data
- 4 sources
- Category
- Materials
What this calculates
The studs in one straight wall from its length and the on-center spacing, the extra studs you enter for corners, intersections and openings, the plate boards, the pieces to order by length and the board feet. With prices you enter it also gives the cost, and with a wall height the area of one face of the wall.
The formula
Layout studs = Wall length ÷ Spacing, rounded up, plus 1. On-center spacing runs from the center of one stud to the center of the next, so the width of the stud does not enter. Put a stud at 0, at one spacing, at two, and so on from one end, then a closing stud at the far end. When the wall is an exact number of spaces the last mark falls on the far end and is that closing stud. When it is not, the last space is shorter than the spacing and the closing stud stands at the end. A 20 ft wall at 16 in is 240 ÷ 16 = 15 spaces and 16 studs. A 13 ft wall at 16 in is 156 ÷ 16 = 9.75, rounded up to 10 spaces, and 11 studs.
The spaces are rounded up once, before the one is added. Adding one first and then rounding up gives the same count. Rounding down and adding one does not: it puts the last stud at 144 in on a 156 in wall and leaves a 12 in bay with no stud at the end, one short. The calculator states the length of the last space when the wall is not a whole number of spaces.
Metric entries are converted exactly (1 ft is 0.3048 m, 1 in is 25.4 mm). A wall shorter than the spacing still has two studs, one at each end.
Corners, intersections and openings are your counts
The framing calculators read for this page (on 2026-09-30) do not give the same counts for a corner, a door or a window, and the right count depends on the framing on your plans. So this calculator adds nothing you do not enter.
Corners: enter how many corners of this wall get extra studs and how many you add at each, beyond the end stud already in the count. Intersections work the same way. Openings: enter how many of each kind, the king, jack and cripple studs each one takes, and the layout studs each one removes, that is, the studs on the spacing that fall inside the opening and are not built. Studs added per opening less studs removed, times the number of openings, is what the openings add or take away. Up to three kinds of opening can be entered. In this calculator a king stud is a full-height stud beside an opening, a jack stud is a stud under an end of the header, and a cripple is a short stud above or below the opening; use the names and the counts on your plans.
What the codes say is quoted in a table with the results, next to your entries. The AWC Wood Frame Construction Manual (2024) 3.4.1.1.3 requires a minimum of three studs at each corner of an exterior wall, with an exception; and 3.4.1.4.2 requires the full-height studs at each end of a header to be not less than half the number of studs the opening replaces, in accordance with Table 3.23C (by header span and stud spacing, and reducible under Table 3.23D). These are design provisions, not a takeoff count: the “layout studs it removes” entry is this calculator’s own way of netting an opening against the layout. The 2024 IRC supports headers with jack studs or approved framing anchors and sets the minimum number of full-height studs at each end of a header in Table R602.7.5, by span and wind. Which of those applies to your wall, and to your jurisdiction, is not decided here.
Spacing, and what the code table says
Stud spacing is your input, from your plans. The calculator does not say which spacing a wall may use, and it does not prefer one. Table R602.3(5) of the 2024 IRC lists the maximum spacing, 16 or 24 in, by stud size, laterally unsupported height and what the wall supports: for 2 × 4 bearing studs at 10 ft, 24 in under a roof-ceiling or habitable attic assembly only and 16 in under one floor plus a roof-ceiling or habitable attic assembly; for 2 × 6, 24, 24 and 16 in for a roof-ceiling or habitable attic assembly only, one floor and two floors. Nonbearing walls have their own columns. Footnotes apply. So the code does not set 16 in as a single rule; it sets a maximum that depends on the wall.
A table of the layout studs for your wall at 12, 16, 19.2 and 24 in, and at your own spacing if it is another, comes with the results. It is plain arithmetic: nothing is ticked, ranked or ruled out. At 19.2 in, a 96 in length divides into exactly five spaces, so an 8 ft wall takes 6 studs.
Plates
You enter the number of bottom and top plate courses. Plate length is the wall length times the courses, and boards per course is the wall length divided by the board length, rounded up; plate boards is boards per course times courses. Each course is counted on its own, so no offcut is carried to the next course and the offset of end joints is not calculated. The wall length is used as entered: no allowance is made for a door opening in the bottom plate or for plates overlapping at corners.
The 2024 IRC (R602.3.2) caps wood stud walls with a double top plate with end joints offset not less than 24 inches (610 mm). Its exception lets a single top plate stand in for the double one on conditions: the single plate is tied at corners, intersecting walls and in-line splices as Table R602.3.2 sets out, and the rafters or joists are centered over the studs within 1 inch (25 mm); the exception also lets the top plate be omitted over headers that are adequately tied to the adjacent wall sections. This calculator checks none of those conditions. R602.3.4 has studs bear on a nominal 2-by or larger plate at least as wide as the studs. The WFCM (3.4.1.2) puts double top plates on exterior stud walls and (3.4.3.2) allows single or double top plates on interior nonloadbearing partitions. The number of courses is yours; plates are counted at the size you enter.
Lumber list and board feet
Pieces to order by length: the studs, each at the stud length you enter, and the plate boards at the board length you enter. The stud length is yours; no wall height is converted to a stud length and no precut length is assumed. Board feet = Pieces × Thickness (in) × Width (in) × Length (ft) ÷ 12, on nominal sizes, the same arithmetic as the board foot calculator. Board feet count the nominal size, not the dressed one: PS 20-25 (§2.2, Table 3) counts a 2x4 as 2 by 4 although a dry 2x4 is dressed to 1 1/2 by 3 1/2 inches, so 5.333 board feet for an 8 ft 2x4 is a count of lumber sold, not a volume of wood.
Nothing in the lumber group starts filled in: the stud length, the nominal size, the plate courses and the plate board length are yours, from your plans. The plates get board feet as soon as you give the size, the courses and the board length, even with no stud length.
Header stock is not counted. Its size comes from your plans and the code’s header tables, which depend on span, load and building width.
Waste, prices and wall area
Waste is a percentage you enter, blank by default, and no typical figure is assumed. It is applied to the studs, to the plate boards and to the panel count, each rounded up once at the end. Prices are yours, one per stud and one per plate board: cost is the quantity to order times the price, each line is rounded to the cent as a supplier’s line total is, the total adds the rounded lines, and each line is shown so it can be multiplied by hand.
Wall face area = Wall length × Wall height − the openings you enter, for one face of the wall. Enter the area of one panel to get a panel count, rounded up. No panel size is assumed, and the seams and how they fall on the studs are not modeled. To add the areas of several openings, use the square footage calculator.
What is deliberately not here
No stud count per corner, per intersection, per door or per window. No spacing judgment and no pass or fail against a code. No header sizes and no precut stud lengths. No waste, price, panel size, stud length, lumber size, plate course count or plate board length unless you enter it. No lateral bracing, wind or seismic check, and no steel studs. The calculator counts lumber; it does not design a wall.
A 20 ft wall, 16 in on center, with counts and a 10% allowance
Every entry here is an example, not a recommendation: the corner and door counts, the waste percentage, the stud and board lengths and the plate courses are what you would type from your own plans.
- Wall length
- 20 ft
- Spacing
- 16 in on center
- Corners
- 2, with 2 studs added at each
- One door
- 2 king, 2 jack, 0 cripple, and it removes 1 layout stud
- Lumber
- 2 × 4 nominal; studs 8 ft; plate boards 8 ft; 1 bottom and 2 top courses
- Waste
- 10%
- 01Spaces= 20 × 12 ÷ 16 = 240 ÷ 16= 15 spaces
- 02Layout studs= 15 + 1= 16 studs
- 03Corner studs= 2 × 2= 4 studs
- 04Opening studs= 1 × (2 + 2 + 0 − 1)= 3 studs
- 05Studs= 16 + 4 + 3= 23 studs
- 06Studs to order= 23 × 1.10 = 25.3, rounded up= 26 studs
- 07Plate length= 20 × 3= 60 ft
- 08Plate boards= (20 ÷ 8 = 2.5, rounded up to 3) × 3= 9 boards; 10 to order
- 09Board feet, studs= 26 × 2 × 4 × 8 ÷ 12= 138.667 bd ft
- 10Board feet, plates= 10 × 2 × 4 × 8 ÷ 12= 53.333 bd ft
26 studs and 10 plate boards, 192 bd ft on the nominal size
Layout studs for a straight wall, by length and spacing
Each cell is the wall length in inches ÷ spacing, rounded up, plus 1: the layout studs only, before any corner, opening or waste count. It is the same arithmetic the calculator uses; nothing is ticked or ruled out.
| Wall length | 12 in | 16 in | 19.2 in | 24 in |
|---|---|---|---|---|
| 4 ft | 5 | 4 | 4 | 3 |
| 6 ft | 7 | 6 | 5 | 4 |
| 8 ft | 9 | 7 | 6 | 5 |
| 10 ft | 11 | 9 | 8 | 6 |
| 12 ft | 13 | 10 | 9 | 7 |
| 16 ft | 17 | 13 | 11 | 9 |
| 20 ft | 21 | 16 | 14 | 11 |
| 24 ft | 25 | 19 | 16 | 13 |
| 30 ft | 31 | 24 | 20 | 16 |
| 40 ft | 41 | 31 | 26 | 21 |
A length that is not a whole number of spaces has a last space shorter than the spacing: 10 ft at 16 in is 7.5 spaces, rounded up to 8, so 9 studs. For 19.2 in, 96 ÷ 19.2 is exactly 5, and so 6 studs.
What it assumes
- 01You enter the wall length and the on-center spacing from your plans. One straight wall at a time.
- 02A stud stands at every mark from one end and a closing stud stands at the far end; the spaces are rounded up once.
- 03Extra studs for corners, intersections and openings, and the layout studs an opening removes, are counted only as you enter them.
- 04Plate courses and the plate board length are yours; each course is counted alone, with no offcut carried over.
- 05Board feet are counted on the nominal size you enter, the way board measure is counted.
- 06The stud length, nominal size, plate courses, plate board length, waste, prices, panel area and wall height start blank and are used only if you enter them.
What it does not do
- It counts one straight wall. For a floor plan, run each wall and add the counts: adding the lengths first rounds once for all of them and misses the ends.
- It does not say whether a wall, a spacing or a count meets a code. The code figures quoted are for reading beside your numbers.
- It counts no headers, sills, blocking, bracing, fireblocking or fasteners.
- It converts no wall height to a stud length and assumes no precut length.
- Plates are counted at the wall length as entered: no reduction for doors, no corner overlap, no end-joint offset.
- Studs at a corner or an opening are only as good as the counts you enter for them.
- Board feet are on nominal sizes and are not the volume of the dressed lumber.
Common questions.
- How many studs do I need for a wall?
- Divide the wall length by the on-center spacing, round up, and add one. A 20 ft wall at 16 in on center is 240 ÷ 16 = 15 spaces, so 16 studs; at 24 in it is 240 ÷ 24 = 10, so 11. That is the layout studs only. Corners, intersections, openings and waste are extra, and you enter them.
- How many studs are in a 12 ft wall?
- 10 at 16 in on center (144 ÷ 16 = 9 spaces, plus 1) and 7 at 24 in (144 ÷ 24 = 6, plus 1), before corners and openings. The table on this page lists other lengths at 12, 16, 19.2 and 24 in.
- Why do I add one?
- The spaces are the gaps between studs; a row of studs always has one more stud than it has gaps. Fifteen spaces need sixteen studs.
- Do I round before or after adding one?
- Rounding up before or after gives the same count, because rounding up a number and adding one is the same as adding one and rounding up. Rounding down does not: a 156 in wall at 16 in is 9.75 spaces, which is 10 spaces and 11 studs when rounded up, but 10 studs when rounded down and one added, and that leaves the last 12 in of wall with no stud at its end.
- How many 2x4 studs do I need for a wall?
- The same count: the stud size does not change the number, because on-center spacing is measured from center to center. A 2x4 and a 2x6 wall of the same length and spacing have the same layout studs. The size sets the board feet: an 8 ft 2x4 is 2 × 4 × 8 ÷ 12 = 5.333 board feet, and a 2x6 is 8.
- How far apart should studs be?
- That depends on the wall, and this page does not decide it. Table R602.3(5) of the 2024 IRC lists a maximum spacing by stud size, laterally unsupported height and what the wall supports: for a 2 × 4 bearing wall at 10 ft, 24 in under a roof-ceiling or habitable attic assembly only and 16 in under one floor plus a roof-ceiling or habitable attic assembly; for a 2 × 4 nonbearing wall at 14 ft, 24 in. Your jurisdiction decides the edition and any amendment, and your plans decide the spacing.
- How many extra studs does a corner, a door or a window take?
- It depends on the framing on your plans, and framing calculators do not give the same counts: the ones read for this page (on 2026-09-30) differ on what a corner, a door and a window add. The AWC Wood Frame Construction Manual (2024) 3.4.1.1.3 requires a minimum of three studs at each corner of an exterior wall, with an exception, and 3.4.1.4.2 requires the full-height studs at each end of a header to be not less than half the number of studs the opening replaces, in accordance with Table 3.23C (by header span and stud spacing). Enter your own counts, and the studs each opening removes from the layout, under Add detail.
- How many studs do openings add if the layout studs inside them are not built?
- The studs added at the opening, less the layout studs it removes, times the number of openings. For example, a door that takes 2 king and 2 jack studs and removes 1 layout stud is a net of 3; your plans decide the counts. If you count every layout stud as built and the opening’s studs as extra, leave “layout studs it removes” blank. Either way the arithmetic is shown line by line.
- How much plate lumber does a wall need?
- The wall length times the courses of plate. One bottom plate and a double top plate is three courses, so a 20 ft wall is 60 ft of plate, and 9 boards of 8 ft when each course is counted on its own (2.5 boards, rounded up to 3, per course). The IRC (R602.3.2) caps wood stud walls with a double top plate; its exception for a single top plate has conditions of its own (ties as Table R602.3.2 sets out, and rafters or joists centered over the studs within 1 inch), which this page does not check. The number of courses here is yours, and blank until you enter it.
- Should I add waste to a stud count?
- That is your choice, and no figure is assumed. Enter a percentage under Add detail, in the Order section, and it is applied to the studs, the plate boards and the panel count, each rounded up once, and shown in the working.
- How many board feet are in a stud wall?
- Pieces × thickness × width × length ÷ 12, on the nominal sizes. Twenty-six 8 ft 2x4 studs are 26 × 2 × 4 × 8 ÷ 12 = 138.667 board feet, and the plates add to that. Board feet count the nominal 2 by 4, not the dressed 1 1/2 by 3 1/2 inches (PS 20-25). The board foot calculator prices lumber by the board foot and covers other sizes.
- Is there a lumber calculator?
- The board foot calculator is the lumber quantity calculator on this site: sizes and pieces in, board feet and linear feet out, with a price per board foot or per thousand board feet. This page turns a wall into a lumber list; for other lumber, use the board foot calculator.
- Does it count steel studs?
- No. The count is the same arithmetic for any stud on a spacing, but the quoted code sections are for wood studs, the board feet are for lumber, and cold-formed steel wall framing has its own section of the IRC (R603), next to the wood section (R602) that is quoted here.
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Ordered by what usually comes next in the same job, not by keyword.