Rebar Weight Chart: Steel Bar Weight per Metre for Every Size

A steel reinforcing bar weighs d²/162 kilograms per metre, where d is the bar diameter in millimetres: 0.395 kg/m for 8 mm, 0.617 kg/m for 10 mm, 0.888 kg/m for 12 mm, 1.579 kg/m for 16 mm and 2.466 kg/m for 20 mm. The full chart below covers 6 to 50 mm per metre, per 12 m bar and per tonne, so you can check schedules and quotes from steel rebar suppliers in the UAE or rebar suppliers in Saudi Arabia.

This page is for quantity surveyors, site engineers, estimators and buyers who turn bar bending schedules into tonnage and tonnage into purchase orders. It explains where the formula comes from, how much a real bar may differ from the chart, how ASTM bar numbers convert, and how to use the numbers on a schedule and an invoice. Grades, certification and mills are covered in our main guide to steel rebar grades, standards and mills in the UAE and Saudi Arabia; this page sticks to weight.

Rebar weight chart: 6 mm to 50 mm

The kg per metre and area values for 6, 8, 10, 12, 16, 20, 25, 32, 40 and 50 mm are the nominal values in Table 2 of Hong Kong's Construction Standard CS2:2012, a government standard covering grade 250, 500B and 500C bars that EMSTEEL lists alongside BS 4449 B500B in its catalogue. The other sizes (14, 18, 22 and 28 mm, which Gulf mills such as Al Rajhi Steel also roll) are calculated with the same density. Per-bar and per-tonne figures are simple arithmetic from the kg per metre column.

We checked every row against two other published tables: the European sizes table on Wikipedia's rebar page (which gives 1.21 kg/m for 14 mm and 4.83 kg/m for 28 mm, matching the calculated values) and the bar area and weight table published by Capital Reinforcing, a UK reinforcement supplier, which agrees to the third decimal for every size it lists (it rounds 10 mm to 0.616 kg/m). CS2:2012 calls 6 mm and 50 mm non-preferred sizes and names 8, 10, 12, 16, 20, 25, 32 and 40 mm as preferred.

Which sizes you can actually buy depends on the mill. EMSTEEL lists straight bars from 8 to 40 mm, Conares lists bars from 8 to 50 mm, and Al Rajhi Steel lists 8, 10, 12, 14, 16, 18, 20, 22, 25, 28, 32 and 40 mm. A size not on the mill's list may mean a longer lead time or a different source.

Where d²/162 comes from

A bar's nominal mass is its nominal cross-sectional area multiplied by the density of steel. CS2:2012 states the basis exactly: nominal mass per metre is calculated from the nominal area "on the basis that steels have a mass of 0.00785 kg/mm² per metre run", which is a density of 7,850 kg/m³.

1. Area of a circle of diameter d (mm): A = π × d² / 4 mm².
2. One metre of bar has a volume of A × 1,000 mm³, which is A × 10⁻⁶ m³.
3. Mass per metre = A × 10⁻⁶ × 7,850 = π × d² × 7,850 / (4 × 10⁶) = 0.0061654 × d² kg/m.
4. 1 / 0.0061654 = 162.2, so mass per metre = d² / 162.2, usually rounded to d² / 162.

Rounding the divisor to 162 makes the result about 0.1% heavier than the standard's table (12²/162 gives 0.889 instead of 0.888 kg/m). That is irrelevant for estimating, but if a supplier's invoice is calculated from nominal mass, ask them to use the standard's tabulated kg per metre, not a rounded formula, so the numbers match your schedule exactly.

The same arithmetic answers the questions people search for on other sizes: a 4 mm rod is 4²/162.2 = 0.099 kg/m, and for flat steel the density gives 7.85 kg per square metre for every millimetre of thickness, so a 10 mm plate weighs about 78.5 kg/m². For plate and sections, buy from structural steel suppliers who publish their own section tables.

How much a real bar can differ from the chart

The chart gives nominal mass. Rolled bars vary, and the product standards allow a tolerance on mass per metre. The tolerance is the reason a weighbridge ticket rarely matches the theoretical weight.

What that means in money: a 25 tonne order of 12 mm B500B bars, invoiced on theoretical weight, is 25 tonnes on paper. If the same bars were weighed, a lot that sits at the edge of the ±4.5% band could be about 1.1 tonnes lighter or heavier. The bars would still comply. This is why the weight basis (theoretical or actual) belongs in every rebar quote, as our main guide sets out under pricing terms.

Underweight bars matter for more than cost. CS2:2012 makes mass per metre a purchaser's test and explains why: "any reduction in mass will mean a lowering in capacity of the steel reinforcing bar". If you sample bars on delivery, weigh a measured length and compare it to the chart and the tolerance for the standard on the mill certificate.

ASTM bar numbers in millimetres and kg per metre

Drawings to ACI 318, and specifications calling for ASTM or SASO ASTM A615 bars, often name bars by ASTM size number. In inch-pound units the number is the diameter in eighths of an inch for sizes 3 to 8, so a No. 4 bar is half an inch. The metric version of ASTM A615M renames each bar by its diameter rounded to the nearest millimetre (a "soft" conversion), so No. 4 becomes No. 13. These are not the same bars as metric 12 or 14 mm bars, and their masses differ.

Diameters, lb/ft and kg/m are from the US size table on Wikipedia's rebar page; we confirmed each kg/m value with d²/162.2 using the nominal diameter, and every row agrees within 0.3%. Two traps follow from the table. First, ASTM No. 10 (9.5 mm, 0.560 kg/m) is about 9% lighter than a 10 mm metric bar (0.617 kg/m), so a schedule that mixes the two systems will be wrong. Second, ASTM No. 13 sits between 12 mm and 14 mm metric bars. Our guide to rebar sizes and bar marks explains how to tell the two systems apart on the bar itself.

Worked example: from a bar bending schedule to tonnage

A bar bending schedule lists each bar mark with its diameter, number of bars and cut length. Tonnage is total length per diameter multiplied by kg per metre. Take a schedule with three bar marks:

The schedule says 5.84 tonnes, but that is not what you order if the bars are cut from 12 m stock. Bar mark 01 at 6.20 m gets one piece per 12 m bar, leaving a 5.80 m offcut, so 240 pieces need 240 stock bars: 240 × 18.95 kg = 4,548 kg of 16 mm bar to deliver 2,350 kg in the structure. Bar mark 02 cuts five 2.10 m pieces from each 12 m bar (10.50 m used), so 900 pieces need 180 stock bars, or 1,918 kg. Bar mark 03 at 11.50 m wastes 0.50 m per bar: 64 stock bars, or 1,894 kg.

The order is 8.36 tonnes for 5.84 tonnes of scheduled steel, unless offcuts are reused for other marks. That gap is why contractors either optimise cutting lists across the whole schedule, order special lengths (EMSTEEL rolls 12 m by default and 6 to 11.5 m on request and approval), or send schedules to a cut-and-bend shop that nests cuts across many projects. The arithmetic also shows why you should compare cut-and-bend quotes on scheduled weight, and stock-bar quotes on stock weight, never one against the other.

Weight per square metre for slabs and mesh

Estimators often need kg per square metre of slab rather than kg per bar. For bars at a regular spacing s (mm), one layer in one direction weighs kg/m × 1,000 / s per square metre. For example, 12 mm bars at 150 mm centres: 0.888 × 1,000 / 150 = 5.92 kg/m² per direction, so a two-way bottom mat is 11.84 kg/m² before laps, chairs and edge bars. For 10 mm at 200 mm: 0.617 × 5 = 3.09 kg/m² per direction. Add laps and wastage from your own project rules, not from a generic percentage.

Once you have the steel weight for a pour, coordinate deliveries with your ready-mix concrete supplier so that fixing, inspection and pouring follow each other closely.

Bundles, coils and delivery weights

Mills ship straight bars in bundles and small sizes also in coil. The published figures differ by mill, so use them for planning only and take the actual weight from the delivery note:

• EMSTEEL (formerly Emirates Steel Arkan): bundle or coil weight 2.0 tons; straight bars in bundles with five straps; length 12.00 m by default with a length tolerance of minus 0, plus 100 mm; coil 8 to 16 mm.
• Conares: coil 6 to 16 mm, coil weight 1.8 to 2.2 tons; bars 6 to 18 m long.
• Qatar Steel: rebar in coil 7, 8, 10, 12, 14 and 16 mm, coil weight 1,050 to 1,200 kg.

The chart turns those weights into counts. A 2.0 tonne bundle of 16 mm bars at 12 m is about 2,000 / 18.95 = 105 bars; a 2.0 tonne coil of 12 mm is about 2,000 / 0.888 = 2,252 m of bar. CS2:2012 also allows +100 mm and minus 0 on ordered length, so a bar ordered at 12 m may be up to 12.1 m long and slightly heavier than the chart's 12 m figure.

Using the chart in an RFQ and on delivery

1. State tonnage per diameter and say whether it is scheduled weight (cut-and-bend) or stock-bar weight.
2. Name the standard and grade, because the mass tolerance follows from them.
3. Ask whether the invoice will use theoretical weight from the standard's table or weighbridge weight, and which kg/m values the supplier uses.
4. Specify bar length (12 m or special lengths) and whether coil is acceptable for small diameters.
5. On delivery, count bars per bundle against the tag, multiply by the chart, and compare to the delivery note.
6. For a mass check, cut a measured length, weigh it, and compare to nominal kg/m within the tolerance for the standard on the certificate.

When your schedule is ready, post your rebar requirement on ListGCC and ask mills, stockists and cut-and-bend shops in the UAE and Saudi Arabia to quote on the same weight basis.

More in this series: Rebar Couplers and Mechanical Splices, GFRP, Epoxy-Coated and Galvanised Rebar for Corrosive Gulf Exposure.

Frequently asked questions

How many kg is a 12mm steel bar?

A 12 mm bar has a nominal mass of 0.888 kg per metre, so a standard 12 m length weighs about 10.66 kg. One tonne of 12 mm bar is about 1,126 m, or roughly 94 bars of 12 m. Under BS 4449 B500B the actual mass per metre may differ from nominal by up to 4.5% either way, so weighed bars can be slightly lighter or heavier.

What is the weight of a 16mm steel bar?

A 16 mm bar weighs 1.579 kg per metre nominal, so one 12 m bar is about 18.95 kg and a tonne holds about 633 m, or roughly 53 bars of 12 m. The value comes from the bar's 201.1 mm² nominal area multiplied by 7,850 kg/m³, the density used in the reinforcing bar standards.

What is the formula for steel bar weight per metre?

Weight per metre in kg = d²/162, where d is the diameter in millimetres. It comes from area (π × d²/4 mm²) multiplied by a steel density of 7,850 kg/m³, which gives 0.0061654 × d², or d²/162.2. For total weight, multiply by the total length in metres. Use the standard's tabulated kg/m for invoices.

How much does a tonne of rebar cover in length?

Divide 1,000 by the mass per metre. A tonne is about 2,532 m of 8 mm, 1,621 m of 10 mm, 1,126 m of 12 mm, 633 m of 16 mm, 406 m of 20 mm, 259 m of 25 mm and 158 m of 32 mm bar. Divide those lengths by 12 to get the approximate number of 12 m bars per tonne.

Is ASTM No. 4 rebar the same as 12mm?

No. ASTM No. 4 (soft metric No. 13) has a nominal diameter of 12.7 mm and weighs 0.994 kg/m, about 12% more than a 12 mm metric bar at 0.888 kg/m. Bars from the two systems have different areas, so they can only be swapped if the structural engineer checks the design and approves the change in writing.

Why does the weighbridge weight differ from the theoretical weight?

Rolled bars are allowed to deviate from nominal mass: ±4.5% for BS 4449 B500B bars from 10 to 40 mm, ±6% for 8 mm, and ±6% for ASTM A615 bars as listed by EMSTEEL. Bars can also be up to 100 mm longer than ordered. Agree in the quote whether you pay on theoretical or weighed tonnage.

How do I calculate rebar weight per square metre of slab?

Multiply the bar's kg per metre by 1,000 and divide by the spacing in millimetres, for each layer and direction. Example: 12 mm bars at 150 mm centres weigh 0.888 × 1,000 / 150 = 5.92 kg/m² in one direction, so a two-way mat is 11.84 kg/m². Then add laps, chairs and edge bars from the drawings.

Sources

• Construction Standard CS2:2012, Steel Reinforcing Bars for the Reinforcement of Concrete (Hong Kong CEDD, PDF)
• EMSTEEL, Reinforcing Bars Product Catalogue (PDF)
• Conares, rebars and rebars in coil
• Rajhi Steel, rebars reinforcement steel
• Qatar Steel, product specifications
• Wikipedia, Rebar (US and European size tables)
• Capital Reinforcing, shape codes and area and weight of bars (PDF)

Featured image: Photo: Gerd Fahrenhorst, CC BY 4.0, via Wikimedia Commons