Free tool: Division 03 reinforcing
Rebar calculator for slabs, footings and walls, with a weight chart
Turn bar size, spacing and dimensions into bars, laps, linear feet, pounds and tons. Add your price per ton to see the cost.
Fixed price in 2 business hours. Pay only after you accept.
- Fixed price agreed before any work starts
- Plan review is free
- You pay only after you accept the price and delivery date
- Single-trade estimates in 48 hours
Quick answer
The Bidmere rebar calculator counts the bars in a slab grid, a continuous footing or a wall from the bar spacing, adds laps where a run is longer than the stock bar, and converts linear feet to pounds and tons with the ASTM standard bar weights. Enter your own price per ton for the cost. It is free and runs in your browser.
Division 03: Concrete reinforcing
Rebar calculator
Bars, laps, linear feet, pounds and tons for a slab grid, a continuous footing or a wall, from bar size and spacing. Price it at your own cost per ton.
Results
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Get a fixed quote Fixed price in 2 business hours. Plan review is free. Pay only after you accept.Need the whole job measured? This calculator covers one area at a time. Send the plans and we return the full takeoff and estimate. Fixed quote within 2 business hours. Plan review is free, and you pay only after you accept.
Get a fixed quoteHow to use the rebar calculator
- Element and bar size. Slab grid, continuous footing or wall, and the bar size from the drawings.
- Dimensions and spacing. Feet for lengths, inches for spacing and footing width.
- Laps, cover and stock length. Enter the lap splice length and cover from the structural drawings; the stock length starts at 60 ft.
- Your costs. Price per ton, placing labor per ton and a lump sum for chairs, tie wire and delivery.
Use one bar size per run. If the two directions of a slab use different bars, run each direction separately.
How the rebar calculator works
| Step | Formula |
|---|---|
| Bars in a grid | Span to fill / spacing (ft), rounded down, + 1 |
| Bar length | Span the bar runs, minus cover at each end |
| Pieces per run | If longer than stock: (run length - lap) / (stock length - lap), rounded up |
| Laps per run | Pieces - 1 |
| Linear feet | Bars x (bar length + laps x lap length) |
| Weight | Linear feet x unit weight (lb per ft) |
| Tons | Pounds / 2,000 |
Spacing is counted from the first bar at the cover line, so a 30 ft span at 12 in holds 31 bars. Hooks, bends and dowels are not counted; add them as separate lines from the bar schedule.
Rebar weight chart: pounds per foot by bar size
These are the nominal weights and diameters of ASTM standard reinforcing bars as South Dakota DOT publishes them in Table 7.1 of its structures manual. The bar number is the diameter in eighths of an inch up to #8.
| Bar size | Weight (lb per ft) | Nominal diameter (in) | Weight of a 20 ft bar (lb) |
|---|---|---|---|
| #3 | 0.376 | 0.375 | 7.5 |
| #4 | 0.668 | 0.500 | 13.4 |
| #5 | 1.043 | 0.625 | 20.9 |
| #6 | 1.502 | 0.750 | 30.0 |
| #7 | 2.044 | 0.875 | 40.9 |
| #8 | 2.670 | 1.000 | 53.4 |
| #9 | 3.400 | 1.128 | 68.0 |
| #10 | 4.303 | 1.270 | 86.1 |
| #11 | 5.313 | 1.410 | 106.3 |
| #14 | 7.650 | 1.693 | 153.0 |
| #18 | 13.600 | 2.257 | 272.0 |
A rebar weight calculator is this table times length: 100 ft of #5 weighs 100 x 1.043 = 104.3 lb.
Rebar calculator for a slab and for footings
For a slab, count the bars each way from the spacing and multiply by the bar length. For a 40 by 30 ft slab with #4 at 12 in each way: 31 bars of 40 ft and 41 bars of 30 ft, 2,470 LF, which is about 1,650 lb or 0.82 tons before laps and waste.
For a continuous footing, multiply the number of continuous bars by the footing length plus laps, then add the transverse bars at their spacing. Three #4 bars in 120 ft of footing, spliced from 60 ft stock with 30 in laps, need 375 LF, about 251 lb.
For the concrete in the same slab or footing, use the concrete calculator.
Why lap length has no default
The Concrete Reinforcing Steel Institute notes that lap length varies with concrete strength, rebar grade, size and spacing, and that ACI 318 requires the engineer to show the location and length of every lap splice on the structural drawings. So the lap is yours to enter, from the drawings.
The stock length starts at 60 ft, the standard length for reinforcing bars according to CRSI. Change it if your supplier stocks shorter bars.
What this rebar calculator does not cover
- Hooks, bends and standard hook extensions
- Dowels, corner bars, trim bars at openings and additional bars
- Bar supports, chairs and tie wire
- Epoxy-coated, galvanized or stainless bars and their prices
- Shop drawings and placing drawings
A plan-based rebar takeoff lists every bar by mark from the schedules. See rebar takeoff and estimating.
Before you send plans
Common questions about handing off the work
Why no lap default?
Lap length is a design value on the drawings, not a rule of thumb.
Can I order from these numbers?
Use them to check a quantity. Orders follow the bar schedule and placing drawings.
Who sets the final price?
You do. Bidmere prices quantities at your rates.
Questions
Frequently asked questions
How much does rebar weigh per foot?
#3 weighs 0.376 lb per ft, #4 0.668, #5 1.043, #6 1.502, #7 2.044, #8 2.670, #9 3.400, #10 4.303 and #11 5.313 lb per ft, as published for ASTM standard reinforcing bars in SD DOT Table 7.1.
How do I calculate rebar for a slab?
Divide each span by the bar spacing, round down and add one bar. Multiply the bars each way by their length, add laps, then multiply the linear feet by the unit weight. A 40 by 30 ft slab with #4 at 12 in each way takes 2,470 LF, about 1,650 lb.
How do I convert rebar linear feet to tons?
Multiply the linear feet by the bar’s weight per foot to get pounds, then divide by 2,000. 2,470 LF of #4 is 2,470 x 0.668 = 1,650 lb, or 0.82 tons.
How long is a lap splice?
It depends on the design. CRSI notes the lap varies with concrete strength, bar grade, size and spacing, and ACI 318 requires the engineer to show lap lengths on the drawings. Enter the lap from your drawings.
What length does rebar come in?
CRSI gives 60 ft as the standard length for reinforcing bars. Suppliers also cut shorter lengths; change the stock length in the calculator to match your order.
Does the calculator store what I enter?
No. It runs in your browser and does not send or save your entries.
Can Bidmere take off the rebar from my drawings?
Yes. Send the structural drawings for a free plan review and a fixed quote within 2 business hours. Single-trade estimates are from $195 and ready in 48 hours after you accept.
For your website
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Sources
- South Dakota DOT Structures Construction Manual, Chapter 7, Table 7.1 (ASTM standard reinforcing bars): https://dot.sd.gov/media/fe553ec1/Chapter7ReinforcingSteel.pdf
- CRSI, Economy of construction (standard bar length): https://www.crsi.org/reinforced-concrete-benefits/economy-of-construction/
- CRSI, Lap splices: https://www.crsi.org/reinforcing-basics/reinforcing-steel/splicing-bars/lap-splices/