Rebar Calculator
Rebar weight, length and bars-per-tonne takeoff for any size list — free.
Enter each rebar size with length and quantity. The calculator computes weight per bar (π/4 × d² × 7850 kg/m³), total tonnes for your order and how many bars make one tonne — for both metric and US imperial sizes.
Rebar weight chart
| Diameter (mm) | kg/m | lb/ft | m per tonne |
|---|---|---|---|
| Ø6 | 0.222 | 0.149 | 4505 |
| Ø8 | 0.395 | 0.265 | 2534 |
| Ø10 | 0.617 | 0.414 | 1622 |
| Ø12 | 0.888 | 0.597 | 1126 |
| Ø14 | 1.208 | 0.812 | 828 |
| Ø16 | 1.578 | 1.061 | 634 |
| Ø20 | 2.466 | 1.657 | 405 |
| Ø25 | 3.853 | 2.589 | 260 |
| Ø28 | 4.834 | 3.248 | 207 |
| Ø32 | 6.313 | 4.242 | 158 |
| Ø40 | 9.865 | 6.629 | 101 |
FAQ
How is rebar weight calculated?
Weight per metre follows the section formula π/4 × d² × 7850 kg/m³, which is the exact form of the classic d²/162 rule of thumb. Results match steel supplier tables within rounding.
Does it include laps and wastage?
No — enter the cut lengths you need. For laps, add the lap length to each bar; for wastage, add a percentage to the quantity (e.g. 3 extra bars per 100).
Can I use US bar sizes?
Yes, the size dropdown includes #3–#11 US bars alongside metric 6–40 mm. US sizes are converted to their metric diameters internally.
How many 12 mm rebar bars are in a tonne?
A 12 mm bar weighs 0.888 kg/m, so one tonne is 1,126 m — about 93 twelve-meter bars. The chart above lists kg/m and bars per tonne for every metric and US size.