Rebar Weight Calculator

Inputs

Bar Size

Total Bar Length (m)

Total length of all bars — bars × cut length, or the sum of every bar on the drawing.

Wastage / Lap Allowance (%)

Typical allowance: 3–5% for laps, cut-offs, and tying waste.

For estimation purposes only. Terms of Use

Result

—

kg per metre of bar

Bar diameter—

Total length—

Weight (no waste)—

With wastage—

6 m sticks needed—

Choose the bar size and enter the total length of bar.

Weight per metre = diameter² ÷ 162 (diameter in mm).

Multiply by total length, add your wastage allowance, and divide by 6 m for sticks.

Formula Used

Weight per metre = Diameter² ÷ 162
Total weight = kg/m × Total length × (1 + Wastage %)

Diameter is in millimetres and the result is in kilograms per metre. This is the standard estimating formula used across the industry.

Worked Example

A slab requires 500 m of #5 bar (15.9 mm) with a 5% wastage allowance.

kg/m = 15.9² ÷ 162 = 1.56 kg/m
Total = 1.56 × 500 = 780 kg
With 5% waste = 780 × 1.05 = 819 kg (0.82 t)

When to Use This Calculator

Use this when estimating reinforcement tonnage for footings, slabs, walls, and paving — ordering rebar, comparing supplier quotes, or checking a quantity takeoff.

When Not to Use This Calculator

This is an estimating tool only. It does not account for bar bending schedules, couplers, chairs, ties, or structural design requirements — verify against approved shop drawings.

Frequently Asked Questions

How much does rebar weigh per metre? ▾

It depends on bar size. A #5 bar (15.9 mm) weighs about 1.56 kg/m, a #8 bar (25.4 mm) about 3.98 kg/m. Use the calculator to check any size instantly.

Why add a wastage allowance? ▾

Laps, cut-offs, and offcuts always add a few percent to the theoretical weight. A 3–5% allowance is typical; increase it for complex layouts with many bars cut to length.