Rebar weight per metre: how to estimate the steel of a job

Weight per metre by diameter

A bar weighs its cross-section × the density of steel (7,850 kg/m³), about d² ÷ 162 with d in mm. Usual values:

• Ø6: 0.222 kg/m · Ø8: 0.395 kg/m · Ø10: 0.617 kg/m
• Ø12: 0.888 kg/m · Ø14: 1.208 kg/m · Ø16: 1.578 kg/m
• Ø20: 2.466 kg/m · Ø25: 3.853 kg/m

Total length, laps and waste

Add up the length of every bar of the same diameter from your plans: number of bars × length of each. Where bars are joined, count the lap length, often 40 to 50 times the diameter; your engineer’s plans give the exact value.

Then add a margin for cutting losses, usually around 5 %, and divide by the bar length sold (often 12 m) to know how many bars to buy.

Worked example

40 bars of 6 m in Ø12, 5 % waste, bars sold in 12 m:

• Length: 40 × 6 = 240 m; with 5 %, 252 m.
• Weight: 252 × 0.888 ≈ 223.7 kg.
• Bars: 252 ÷ 12 = 21 bars of 12 m.
• Stirrups in Ø8, 150 m in total: 157.5 m with waste, about 62 kg, 14 bars.

Good practice

Estimate each diameter separately, then add the weights for the order. Keep the bar schedule of the plans as the reference: cover, anchorage and spacing are structural choices that only the design can set.

The concrete calculator gives the volume and the cement, sand and gravel of the same elements.