All calculators

Behind the numbers— the arithmetic, sourced.

What each quantity means, how it is calculated, and where the figures that are not arithmetic actually come from. Every page supports specific calculators and carries its sources.

01
Soil compaction, shrinkage and swell
Two different factors for the same soil, and published tables that disagree with one another. What FHWA, DOT and textbook tables actually say, the ±33% caveat two of them carry, and the arithmetic.
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CONTENT-MAP B3 · updated 2026-09-30
02
Bank vs loose cubic yards
A bank yard is earth in the ground; a loose yard is the same earth in a truck, and there is more of it. Swell, load factor and the three volumes on one job.
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CONTENT-MAP B1 · updated 2026-09-30
03
How thick should a concrete slab be
The IRC and IBC set 3 1/2 in for concrete floor slabs on the ground and, in the sections reviewed, nothing for driveways or patios. Four local and state documents quoted with the part of the driveway each covers, and how thickness changes the concrete you order.
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CONTENT-MAP B13 · updated 2026-09-29
04
Rebar size chart
Nominal diameter, area and weight per foot of bars #3 to #18 from state DOT tables, the soft-metric sizes #10 to #57, metric conversions, and where the published tables disagree.
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- Rebar
- Concrete
CONTENT-MAP B12 · updated 2026-09-29
05
How to calculate rebar for a concrete slab
Count the bars each way from the spacing and cover, add the lengths, weigh them from a published bar table, and count the sticks after splices. Worked for a slab, with the inputs only your drawings can supply.
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CONTENT-MAP B11 · updated 2026-09-29
06
Excavation volume with sloped sides
The prismoidal formula worked for a pit with battered walls, and how far off the common shortcuts are: averaging the top and base, or ignoring the slope.
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CONTENT-MAP B10 · updated 2026-09-29
07
How to calculate trench volume
Trench volume is the cross-section times the length. Vertical and sloped walls, why laying the walls back adds volume quickly, and how spoil and backfill differ from the excavation.
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CONTENT-MAP B9 · updated 2026-09-29
08
Tri-axle dump truck capacity
Legal weight comes from a published federal formula on the axles, and the load is what is left after the truck’s own weight. The bridge formula, worked.
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CONTENT-MAP B8 · updated 2026-09-29
09
Gravel driveway depth
No national standard for gravel driveway depth was found in the sources reviewed. What the FHWA handbook and the Gravel Roads manual say for unpaved roads, why a driveway differs, and how any depth becomes yards and tons.
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CONTENT-MAP B5 · updated 2026-09-29
10
Dump truck capacity in cubic yards
Two limits decide how many yards a truck carries — the body volume on its plate and the payload its weight rating allows. The material decides which one binds. Includes dump-body specifications as two manufacturers print them.
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CONTENT-MAP B4 · updated 2026-09-29
11
How cut and fill is calculated
The grid method step by step, the average-end-area and prismoidal formulas for cross-sections, and why area times average depth gets a balanced site wrong.
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CONTENT-MAP B2 · updated 2026-09-03
12
Markup vs margin in construction
Markup is a percentage of cost, margin is a percentage of price. The conversion formulas, a worked example and the full table.
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CONTENT-MAP B6 · updated 2026-09-01