Steel Bar Weight Calculator — How Heavy Is That Rebar?
Steel is ordered by weight but used by length — and that gap is where money leaks. A supplier’s challan says 2.5 tonnes; your count says 130 bars of 16 mm. Are they the same? The steel bar weight calculator answers in seconds: pick the bar size (or enter a custom diameter), enter the length, and get the exact weight in kilograms. Site engineers use it three ways — estimating steel for a BBS, checking deliveries at the gate, and converting a bar bending schedule into a purchase order.
Steel Bar Weight Calculator
Select bar size or custom diameter. Enter length to calculate weight in your preferred unit system.
How to Use This Steel Bar Weight Calculator
- Select the bar size — 6, 8, 10, 12, 16, 20, 25, 28, 32 or 40 mm. Or enter a custom diameter if your bar isn’t listed.
- Enter the length — per bar, or the total running length from your BBS.
- Choose the length unit — metres or feet.
- Read the steel weight in kg. Multiply by the number of bars for bundle or delivery totals.
Steel Bar Weight Formula (How the Calculator Works)
The calculator uses the standard site formula:
Weight (kg/m) = D² ÷ 162 — where D is the bar diameter in mm.
This comes from the physics: weight = cross-sectional area × length × density of steel (7,850 kg/m³). For a 1-metre bar: (π/4 × D² ÷ 1,000,000) × 7,850 = D² ÷ 162.19, rounded to D²/162 for site use.
To get total weight: total kg = (D²/162) × length in metres × number of bars.
Worked Examples
Example 1 — one 12 mm bar, 12 m long: Weight per metre = 12² ÷ 162 = 144 ÷ 162 = 0.888 kg/m. Total = 0.888 × 12 = 10.66 kg.
Example 2 — checking a delivery: 25 bars of 16 mm, 12 m each: Weight per metre = 16² ÷ 162 = 256 ÷ 162 = 1.579 kg/m. Total = 1.579 × 12 × 25 = 473.7 kg (≈ 0.474 tonne). If the challan claims 550 kg for these 25 bars, something is off — recount or weigh before signing.
Example 3 — from BBS to purchase order: Your bar bending schedule totals 850 running metres of 20 mm bar. Weight = (20² ÷ 162) × 850 = 2.466 × 850 = 2,096 kg ≈ 2.1 tonnes. Add 5% wastage for laps and cutting → order 2.2 tonnes.
Steel Bar Weight Table (kg per metre)
| Bar dia (mm) | Weight (kg/m) | Weight of 12 m bar (kg) | Bars per tonne (12 m) |
|---|---|---|---|
| 6 | 0.222 | 2.66 | 376 |
| 8 | 0.395 | 4.74 | 211 |
| 10 | 0.617 | 7.40 | 135 |
| 12 | 0.888 | 10.66 | 94 |
| 16 | 1.579 | 18.95 | 53 |
| 20 | 2.466 | 29.59 | 34 |
| 25 | 3.853 | 46.24 | 22 |
| 28 | 4.834 | 58.01 | 17 |
| 32 | 6.313 | 75.76 | 13 |
| 40 | 9.865 | 118.38 | 8 |
Standard bar length is 12 m (about 40 ft). Bars-per-tonne helps you verify a full bundle at a glance.
Common Bar Uses on Site (Quick Reference)
| Bar size | Typical use |
|---|---|
| 6 mm | Stirrup rings are usually 8–10 mm; 6 mm for light ties |
| 8–10 mm | Stirrups, ties, distribution steel in slabs |
| 12 mm | Slabs, beams (main steel in small spans) |
| 16–20 mm | Beams, columns — the workhorse sizes |
| 25 mm and above | Heavy columns, foundations, bridges |
Steel Estimation Thumb Rules (Early Budgeting)
| Element | Thumb rule |
|---|---|
| RCC slab (with beams) | 3.5–4.5 kg per sq ft |
| RCC column | 8–12 kg per running ft of column height (depends on size) |
| Footings | 3–5 kg per sq ft of footing area |
| Overall RCC frame building | 4–6 kg per sq ft of covered area |
These are budgeting rules only — the structural design and BBS give the final figure. But when a client asks “how much steel for a 1,000 sq ft house?” on the phone, 4,000–5,000 kg is your honest instant answer, and the steel bar weight calculator confirms the exact figure once the BBS is ready.
Field Tips for Steel Weight
- Verify at the gate. Count the bars, note the diameter and length, and run the D²/162 check before the truck leaves. Weighing disputes after unloading never end well.
- Weigh one sample bar. A 12 m bar of 12 mm should weigh ~10.66 kg on a platform scale. If it weighs 9 kg, the bars are under-rolled — reject or renegotiate.
- Remember binding wire. Order 8–10 kg of binding wire per tonne of steel; it never appears in the BBS but the work stops without it.
- Standard length is 12 m. If your supplier delivers 11.8 m bars (it happens), recalculate — 20 cm short on every bar of a 2-tonne order is real money.
- Weight is the same for Fe-415 and Fe-500. Grade changes strength, not density — the weight formula doesn’t care about grade.
Frequently Asked Questions
What is the formula for steel bar weight? Weight (kg/m) = D²/162, where D is the diameter in mm. Multiply by length in metres for total weight.
How much does a 12 m bar of 16 mm weigh? 1.579 kg/m × 12 m = 18.95 kg.
How many 12 mm bars are in one tonne? About 94 bars of 12 m length (1,000 ÷ 10.66).
Does the calculator work for a custom diameter? Yes — enter any diameter in mm (for example 14 mm or 18 mm, common in some markets) and the length; the tool applies the same D²/162 formula.
Is bar weight different for Fe-500 vs Fe-415? No. Weight depends only on diameter, length, and steel density (7,850 kg/m³). Grade affects strength, not weight.
How do I check if the supplier delivered the right weight? Count bars × standard weight per bar from the table above, and compare with the challan. For large orders, weigh one full bundle on a weighbridge.
How much steel do I need per square foot of slab? Rough thumb rule: 3.5–4.5 kg per sq ft of RCC slab including beams (varies with design). Always follow the structural drawings and BBS for the real figure — the thumb rule is only for early budgeting.
What is 1 tonne of steel in maunds? 1 maund = 40 kg in Pakistan, so 1 tonne = 25 maunds.
Final Thoughts
The steel bar weight calculator is a small tool that prevents large losses — run every delivery through D²/162, keep the weight table taped inside the site office, and never sign a challan you haven’t verified. Steel is the costliest material on most RCC jobs; weighing it correctly is the cheapest quality control there is.
Written by Mohsin Raza Adil — BSc Civil Engineering Technologist (NTC-registered), Pakistan.