Rebar Weight Calculator
Reinforcing bar is bought and priced by weight, but drawings and takeoffs give it as a size and a length. This calculator bridges the two: it tells you the unit weight of any bar in kg/m or lb/ft, then adds up a full bar schedule into a single steel weight in kilograms, tonnes or US short tons.
It works in two parts on one page. The weight reference chart lists every standard bar size — 6 mm to 50 mm metric, #3 to #18 imperial — with its nominal mass. The bar schedule below lets you enter each bar as size × length-per-bar × count, and the results panel sums every row into a grand total plus a per-size subtotal so you can see how much of each diameter you need.
All weights are nominal, based on a steel density of 7850 kg/m³. This is a pure weight and quantity tool — for cutting lengths, bend deductions and shape codes, use the bar bending schedule calculator instead.
How to use the rebar weight calculator
Choose metric or imperial units at the top of the page. Metric shows bar sizes in millimetres with weights in kg/m and totals in kg and tonnes; imperial shows # bar designations with weights in lb/ft and totals in pounds and US short tons. Your choice is remembered in your browser.
Read the unit weight of any bar directly from the weight reference chart, or add bars to the schedule to total them. Each schedule row takes a bar size, the length of a single bar, and how many identical bars there are.
Pick a standard size from the dropdown, or choose Custom to weigh a non-standard diameter with the same formula. The row weight updates as you type, and the results panel keeps a running grand total and a per-size breakdown.
Switching units converts your existing bars to the nearest equivalent size and length so you don't lose your schedule.
How to calculate rebar weight in 5 steps
- Choose unitsSelect metric (mm bars, kg/m, kg and tonnes) or imperial (# bars, lb/ft, pounds and US short tons) at the top of the page.
- Find your bar sizeRead the unit weight of any bar straight from the weight reference chart, or note the size you need for the schedule.
- Add bars to the scheduleAdd one row per distinct bar. Pick a standard size or choose Custom to enter a non-standard diameter.
- Enter length and countFor each row, enter the length of a single bar and how many identical bars there are. The row weight updates as you type.
- Read the total weightThe results panel shows the grand total in kg and tonnes (or pounds and short tons) plus a per-size subtotal for ordering.
The rebar weight formula
The nominal mass of a round reinforcing bar comes from its cross-sectional area and the density of steel. For a bar of diameter d in millimetres, the weight per metre is d² ÷ 162.2, which is the same as d² × 0.006165. The constant 162.2 already folds in the area of a circle and a steel density of 7850 kg/m³.
For example, a 12 mm bar weighs 12² ÷ 162.2 = 0.888 kg/m, and a 25 mm bar weighs 25² ÷ 162.2 = 3.854 kg/m. Multiply the unit weight by the total length of that bar to get its weight.
In imperial units the equivalent formula is lb/ft = 2.67 × d², where d is the diameter in inches, matching the ASTM A615 nominal masses. A #8 bar (1 in diameter) weighs 2.67 × 1² = 2.67 lb/ft.
These are nominal figures. Real bars carry deformation ribs and mill rolling tolerances, so an as-delivered bundle can differ slightly from the nominal weight.
Rebar weight chart
The chart below lists the nominal unit weight of every standard bar size, in both kg/m and lb/ft, so you can look up a figure without adding a schedule. These are the same values the calculator uses.
All figures are nominal, based on a steel density of 7850 kg/m³. Multiply the unit weight by a bar's length to get its weight, or use the schedule above to total many bars at once.
Metric bars (BS 4449 / ISO 6935-2)
| Bar size | Diameter | Weight (kg/m) | Weight (lb/ft) |
|---|---|---|---|
| 6 mm | 6 mm | 0.222 | 0.149 |
| 8 mm | 8 mm | 0.395 | 0.265 |
| 10 mm | 10 mm | 0.616 | 0.414 |
| 12 mm | 12 mm | 0.888 | 0.597 |
| 16 mm | 16 mm | 1.579 | 1.061 |
| 20 mm | 20 mm | 2.466 | 1.657 |
| 25 mm | 25 mm | 3.854 | 2.590 |
| 32 mm | 32 mm | 6.313 | 4.242 |
| 40 mm | 40 mm | 9.864 | 6.628 |
| 50 mm | 50 mm | 15.413 | 10.357 |
Imperial bars (ASTM A615)
| Bar size | Diameter | Weight (kg/m) | Weight (lb/ft) |
|---|---|---|---|
| #3 | 9.5 mm | 0.560 | 0.376 |
| #4 | 12.7 mm | 0.994 | 0.668 |
| #5 | 15.9 mm | 1.552 | 1.043 |
| #6 | 19.1 mm | 2.235 | 1.502 |
| #7 | 22.2 mm | 3.042 | 2.044 |
| #8 | 25.4 mm | 3.973 | 2.670 |
| #9 | 28.7 mm | 5.060 | 3.400 |
| #10 | 32.3 mm | 6.404 | 4.303 |
| #11 | 35.8 mm | 7.907 | 5.313 |
| #14 | 43 mm | 11.384 | 7.650 |
| #18 | 57.3 mm | 20.239 | 13.600 |
Nominal mass, based on steel density 7850 kg/m³ (metric d²/162.2, imperial 2.67·d²).
Frequently asked questions
How much does rebar weigh?
It depends on the diameter. A 10 mm bar weighs about 0.616 kg per metre, a 12 mm bar 0.888 kg/m, a 16 mm bar 1.579 kg/m and a 25 mm bar 3.854 kg/m. In imperial, a #4 bar weighs 0.668 lb/ft and a #8 bar 2.67 lb/ft. Look up any size in the weight chart, then multiply by the total length to get the weight.
What is the formula for rebar weight per metre?
For a bar of diameter d in millimetres, weight per metre = d² ÷ 162.2 (the same as d² × 0.006165). The constant 162.2 combines the cross-sectional area of a circle with a steel density of 7850 kg/m³. In imperial units, weight per foot = 2.67 × d² where d is in inches.
How much does 12 mm rebar weigh per metre?
A 12 mm reinforcing bar weighs 0.888 kg per metre (12² ÷ 162.2), which is about 0.597 lb/ft. A standard 12 m length therefore weighs about 10.66 kg. Enter 12 mm bars in the schedule to total any number of them.
How do I calculate the total weight of a bar schedule?
Add a row for each bar: choose the size, enter the length of a single bar and the number of identical bars. The calculator multiplies unit weight × length × count for every row and sums them into a grand total in kg and tonnes (or pounds and short tons), with a per-size subtotal so you can order each diameter.
How do I get rebar weight per foot?
Switch the calculator to imperial units. The weight chart then shows each # bar size in lb/ft — for example #4 at 0.668 lb/ft, #5 at 1.043 lb/ft and #8 at 2.67 lb/ft — matching the ASTM A615 nominal masses. The schedule totals then read out in pounds and US short tons.
What is the difference between metric and imperial rebar sizes?
Metric bars are named by their nominal diameter in millimetres (6, 8, 10, 12, 16, 20, 25, 32, 40, 50 mm). Imperial bars use a # designation where the number is roughly the diameter in eighths of an inch — a #4 bar is 4/8 in (0.5 in). This calculator shows the soft-metric diameter alongside each imperial size as a label, but keeps them as two separate size systems.
Is this the nominal or the actual weight of rebar?
All weights here are nominal, based on a plain round bar and a steel density of 7850 kg/m³. Real reinforcing bar has deformation ribs and is subject to mill rolling tolerances, so a delivered bundle can weigh slightly more or less than the nominal figure. Nominal weight is the standard basis for takeoffs, ordering and pricing.
How do I convert a length of rebar into tonnes?
Multiply the total length by the bar's unit weight to get kilograms, then divide by 1000 for tonnes. For example, 500 m of 16 mm bar is 500 × 1.579 = 789.5 kg ≈ 0.79 t. The schedule does this automatically and shows the tonnage total for you.
Is the calculator private?
Yes. Every calculation runs entirely in your browser. Nothing you enter is sent to any server, and your schedule is saved only in your own browser's local storage.