Rebar Calculator: 22 Bars for a 40 ft Foundation Wall

What does rebar needed 22 bars mean?

It means twenty-two bars reinforce a 40 ft foundation wall once cutting and lap waste is allowed for. The wall itself is 40 feet long; at one bar every 24 inches the bare count is 20 bars, and the 10% waste allowance adds 2 bars for the bars cut at the ends and the laps where bars join, taking the order to 22 bars, or 176 feet of bar in total. The waste bars are not spare stock exactly — they are the bars the wall consumes in cutting and lapping, so a wall ordered without them comes up short at the last bay.

Output · formula · meaning

Three things to check before you trust the number

First, check the spacing figure against the plans: 24 in is a planning figure, but a structural drawing can call for 12 in or 16 in, and at 12 in this wall needs 44 bars, not 22 — spacing moves the whole order. Second, measure the wall the bars run along, not the footing: the count follows the wall length, and an opening the bars skip should come off the length first. Third, judge the waste honestly: a straight run fits 10%, but a wall with many corners and laps can want 15%, since every lap is bar consumed.

Worked example

40 ft long, 24 in spacing, 8 ft bars, 10% waste. Bars exact: 40 × 12 ÷ 24 = 20. With waste: 20 × 1.10 = 22 bars. Total length: 22 × 8 = 176 ft. In practice that means ordering 22 bars of 8 ft, and expecting the last bars to go on the laps and the end cuts. If the same wall used 12 in spacing instead, the need would rise to 44 bars with waste, but the wall covered would be identical.

Every branch, checked

With a 60 ft long wall instead of 40 ft, the bar count rises to 33 bars with waste, or 264 ft total. With 12 in spacing, the count rises to 44 bars with waste, or 352 ft total. With 10 ft bars, the count stays 22 bars but the total rises to 220 ft. With 0% waste, the count falls to 20 bars, or 160 ft total. Wall length, spacing, bar length and waste each move the order on their own, so a wrong spacing is as costly as a wrong measurement.

The reverses, worked backwards

The length behind 22 bars is 40 ft: at 30 ft the need is 17 bars (136 ft total, 30 ft wall, 24 in spacing, 10% waste); at 60 ft it is 33 bars (264 ft total, 60 ft wall, 24 in spacing, 10% waste). The spacing behind 22 bars is 24 in: at 12 in the need is 44 bars (352 ft total, 40 ft wall, 12 in spacing, 10% waste); at 48 in it is 11 bars (88 ft total, 40 ft wall, 48 in spacing, 10% waste). The waste behind 22 bars is 10%: at 0% the need is 20 bars (160 ft total, 40 ft wall, 24 in spacing, 0% waste); at 20% it is 24 bars (192 ft total, 40 ft wall, 24 in spacing, 20% waste). Each reverse moves one input and holds the rest, so the step is exactly one dimension or one waste change.

What the defaults assume

The defaults assume a 40 ft straight foundation wall, bars every 24 in, 8 ft bars, and 10% cutting and lap waste. They do not assume a second layer of bars, horizontal bars, corner bars, chairs or ties — a wall with a second layer needs that layer counted separately, and the ties are bought by the bag, not by the bar.

Who uses this

• A homeowner pouring a foundation wall: the 22-bar order settles the steel call before the concrete truck is booked.
• A DIY builder footing a garden wall: the same maths on the wall alone gives the bars, not a whole house.
• A contractor quoting a job: wall length, spacing, waste — the quote follows the same three steps, and the waste line shows the client why.
• A landlord budgeting a foundation repair: the wall size off the plans, divided by spacing, gives the rebar line on the repair budget.

Accuracy & limitations

The arithmetic is exact for the inputs entered; the judgement is the spacing figure and the waste allowance. Real walls have openings, corners and laps, and the spacing on the structural drawing overrides any planning figure; a wall measured gross over-orders, and a spacing read off a different drawing under-orders. Treat 22 bars as the planning order for a straight 40 ft wall at 24 in spacing, and raise the waste to 15% for a wall with many corners and laps.

Cite this calculator

Bright Side Kit, “Rebar Calculator: 22 Bars for a 40 ft Foundation Wall”, https://brightoolbox.com/rebar-calculator/, accessed 3 November 2026. Students and researchers: cite the calculator name, the page URL and the date you used it, and quote the defaults (40 ft wall, 24 in spacing, 8 ft bars, 10% waste) so the 22-bar result can be checked.

Frequently asked questions