Materials & quantities
Steel & rebar weight calculator
Calculate weights for round bars, plates, hollow sections and entered section masses.
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What a steel and rebar weight calculator does
A steel and rebar weight calculator finds the weight of steel from its cross-section, length and density: weight = cross-sectional area × length × density × quantity. Choose round bar or rebar, round tube, plate or rectangular solid, rectangular hollow section, or a known mass per length, and it returns the weight per foot, the weight of one piece and the total in pounds and US tons (kilograms and tonnes in metric).
For reinforcing bar, enter the nominal diameter. A #4 bar is 0.500 in in diameter, and at a steel density of 490 lb/ft³ that gives 0.668 lb/ft, the ASTM A615 nominal weight. Ten 20 ft #4 bars weigh 133.6 lb.
The shapes are idealized: plain circles and rectangles with square corners. Real rebar has deformations, hollow sections have rounded corners, and all rolled steel has tolerances. For common wide-flange beams and channels pick them from the Standard section library, whose masses come from the designation itself; for angles, HSS and other commercial sections, enter the published weight per foot with the Known mass per length option. Rebar sizes use the nominal masses from ASTM A615, AS/NZS 4671 and BS 4449. The tool does not size reinforcement, check laps or check structure.
How to use the steel & rebar weight calculator
- Choose Imperial or Metric, then choose a Section: Round bar / rebar, Rebar size table, Standard section library, Round tube, Rectangular solid / plate, Rectangular hollow, Known mass per length, or Bar bending schedule.
- Enter the Length of one piece and the Quantity of pieces.
- Enter the dimensions the section asks for: Outside diameter for bars and tubes, Outside width and Outside height / plate thickness for plates and hollow sections, and Wall thickness for tubes and hollow sections. For the rebar table pick a Bar size (US #3–#18, AS/NZS N10–N40 or EU/UK B500 6–40 mm); for the library pick a Section whose mass is in its designation (AISC W and C shapes, UK UB, UC and PFC, AU UB); for a known section, enter the supplier's weight per foot.
- Leave Material density at 490 lb/ft³ (7,850 kg/m³) for carbon steel, or change it for another metal. Add an optional price per lb to get a cost.
- For a Bar bending schedule, fill the schedule table with a bar mark, bar size, shape or bend, cut length per bar and number of bars, using Add bar mark for each mark. The result table is the schedule and the CSV export.
- Read the section mass per foot, the mass of one piece and the total in lb and US tons, or the schedule totals. Download the PDF or CSV, or copy the result into a takeoff or shipping note.
Worked example
Imperial: A ½ in round bar at 490 lb/ft³ weighs approximately 0.668 lb/ft; ten 20 ft bars weigh 133.6 lb.
Metric: A 12 mm round bar at 7,850 kg/m³ weighs approximately 0.888 kg/m; ten 6 m bars weigh 53.27 kg.
Rebar weight chart: #3 to #11 (ASTM A615)
US reinforcing bars are numbered by nominal diameter in eighths of an inch: a #5 bar is 5/8 in. ASTM A615/A615M (Table 1) lists a nominal diameter, cross-sectional area and weight for each size, along with a soft-metric designation (#5 is also marked 16). The weights below are those nominal values.
Entering the nominal diameter in the calculator at 490 lb/ft³ reproduces these weights to within 0.2%. If you need to match the table exactly, use Known mass per length and type in the nominal lb/ft.
| Bar size | Metric size | Nominal diameter | Nominal area | Nominal weight | Weight of a 20 ft bar |
|---|---|---|---|---|---|
| #3 | #10 | 0.375 in (9.5 mm) | 0.11 in² | 0.376 lb/ft (0.560 kg/m) | 7.52 lb |
| #4 | #13 | 0.500 in (12.7 mm) | 0.20 in² | 0.668 lb/ft (0.994 kg/m) | 13.36 lb |
| #5 | #16 | 0.625 in (15.9 mm) | 0.31 in² | 1.043 lb/ft (1.552 kg/m) | 20.86 lb |
| #6 | #19 | 0.750 in (19.1 mm) | 0.44 in² | 1.502 lb/ft (2.235 kg/m) | 30.04 lb |
| #7 | #22 | 0.875 in (22.2 mm) | 0.60 in² | 2.044 lb/ft (3.042 kg/m) | 40.88 lb |
| #8 | #25 | 1.000 in (25.4 mm) | 0.79 in² | 2.670 lb/ft (3.973 kg/m) | 53.40 lb |
| #9 | #29 | 1.128 in (28.7 mm) | 1.00 in² | 3.400 lb/ft (5.060 kg/m) | 68.00 lb |
| #10 | #32 | 1.270 in (32.3 mm) | 1.27 in² | 4.303 lb/ft (6.404 kg/m) | 86.06 lb |
| #11 | #36 | 1.410 in (35.8 mm) | 1.56 in² | 5.313 lb/ft (7.907 kg/m) | 106.26 lb |
Metric bar weight: the d²/162 rule
For a round steel bar at 7,850 kg/m³, mass in kg/m = d² ÷ 162, with d in millimetres. It comes from π/4 × d² × 7,850 ÷ 1,000,000, which simplifies to d² ÷ 162.2. A 12 mm bar is 144 ÷ 162 = 0.889 kg/m, and a 6 m length weighs about 5.33 kg.
The shortcut runs slightly heavy (about 0.1%) and is close enough for site checks. The calculator uses the exact circular area, so its figures are a hair lower than the rule of thumb.
| Bar diameter | d²/162 | Exact (calculator) | 12 m bar |
|---|---|---|---|
| 6 mm | 0.222 kg/m | 0.222 kg/m | 2.66 kg |
| 8 mm | 0.395 kg/m | 0.395 kg/m | 4.74 kg |
| 10 mm | 0.617 kg/m | 0.617 kg/m | 7.40 kg |
| 12 mm | 0.889 kg/m | 0.888 kg/m | 10.65 kg |
| 16 mm | 1.580 kg/m | 1.578 kg/m | 18.94 kg |
| 20 mm | 2.469 kg/m | 2.466 kg/m | 29.59 kg |
| 25 mm | 3.858 kg/m | 3.853 kg/m | 46.24 kg |
| 32 mm | 6.321 kg/m | 6.313 kg/m | 75.76 kg |
| 40 mm | 9.877 kg/m | 9.865 kg/m | 118.38 kg |
Steel density and plate weight per square foot
Carbon steel is taken as 490 lb/ft³ in US practice and 7,850 kg/m³ in metric; the two agree within rounding (490 lb/ft³ is 7,849 kg/m³). One square inch of steel section weighs 490 ÷ 144 = 3.40 lb per foot of length, which is a handy check: a #4 bar with a nominal area of 0.20 in² is 0.20 × 3.40 = 0.68 lb/ft, close to its 0.668 lb/ft nominal weight.
Plate follows the same logic. Each inch of thickness weighs 40.83 lb/ft², or 7.85 kg/m² per millimetre. A 4 × 8 ft sheet of 1/2 in plate is 32 ft² × 20.42 = 653 lb, which matches the calculator with a width of 48 in, a thickness of 0.5 in and a length of 8 ft.
For other metals, change the density. Aluminum is about 2,700 kg/m³ (168.6 lb/ft³), roughly a third of steel, and stainless steels are slightly heavier than carbon steel, typically around 8,000 kg/m³. Use the alloy's published density where the difference matters.
| Thickness | Weight per ft² | 4 × 8 ft sheet |
|---|---|---|
| 1/8 in | 5.10 lb | 163.3 lb |
| 3/16 in | 7.66 lb | 245.0 lb |
| 1/4 in | 10.21 lb | 326.7 lb |
| 3/8 in | 15.31 lb | 490.0 lb |
| 1/2 in | 20.42 lb | 653.3 lb |
| 3/4 in | 30.63 lb | 980.0 lb |
| 1 in | 40.83 lb | 1,306.7 lb |
Worked example: rebar weight for a 20 × 30 ft slab
The drawings call for #4 bars at 12 in on center each way, with 3 in of clear cover at the slab edges. Bar size, spacing and cover come from the engineer or the applicable code; the calculator only weighs what is specified. Each bar is 6 in shorter than the slab (3 in off each end), and the number of bars is the available width divided by the spacing, rounded up, plus one. Enter each direction as a separate calculation:
- Bars running 30 ft: (240 − 6) ÷ 12 = 19.5, rounded up to 20 spaces, so 21 bars at 29 ft 6 in. The calculator returns 413.9 lb.
- Bars running 20 ft: (360 − 6) ÷ 12 = 29.5, rounded up to 30 spaces, so 31 bars at 19 ft 6 in. The calculator returns 403.9 lb.
- Total: 1,224 linear feet and about 818 lb, or 0.41 US tons, before laps, supports and waste.
- Laps: 29 ft 6 in bars are longer than common 20 ft stock, so each needs a lap splice. The lap length comes from the structural drawings; add it to the bar length or count it as extra bars.
Who it is for and when to use it
Rebar takeoffs and orders
Convert bar counts and lengths from the drawings into weight for ordering, pricing by the pound or ton, or checking a fabricator's bar list.
Shipping, lifting and handling
Check the weight of a bundle of bars, a stack of plate or a load of tube against a truck, trailer, hoist or crane limit.
Fabrication estimates
Price a plate, tube or bar job by weight using your supplier's price per pound, with the quantity of pieces built in.
Totaling commercial sections
Enter the published weight per foot of a beam, angle or channel to total a steel list without modelling the shape.
Method, formulas & assumptions
Weight = cross-sectional area × length × density × quantity; round area = πd²/4 and tubes subtract the inner section. Bar-size and section presets use nominal mass per length from ASTM A615, AS/NZS 4671, BS 4449 / EN 10080 and the section designation. A bar bending schedule sums cut length × bars × nominal mass per mark.
Imperial inputs are converted with exact factors (1 ft = 0.3048 m, 1 lb = 0.45359237 kg, 1 US gal = 3.785411784 L) before the calculation runs in SI, then results are converted back.
Common mistakes to avoid
- Entering the bar number as the diameter. A #5 bar is 0.625 in, not 5 in or 5 mm.
- Measuring rebar across the deformations. Rebar weight is based on the nominal diameter, which is smaller than a caliper reading over the ribs.
- Leaving out lap splices, hooks and bends. They add length to every continuous or hooked bar; take them from the drawings.
- Treating the idealized hollow-section weight as exact. Real tubes have rounded corners and tolerances; use the manufacturer's published weight per foot for ordering.
- Mixing US tons and metric tonnes. A US ton is 2,000 lb (0.907 t); a metric tonne is 2,204.6 lb.
- Forgetting to change the density for aluminum or stainless steel. The default is carbon steel.
Scope & limits
Idealized sections exclude rolling tolerances, ribs and corner radii; presets are nominal values. Schedule cut lengths must include hooks, bends and laps. Use a supplier kg/m value for other commercial sections. No reinforcement sizing or structural checks.
Frequently asked questions
How much does #4 rebar weigh per foot?
#4 rebar weighs 0.668 lb/ft (0.994 kg/m) per ASTM A615. A 20 ft bar weighs 13.36 lb.
How much does #5 rebar weigh?
#5 rebar weighs 1.043 lb/ft (1.552 kg/m). A 20 ft bar weighs about 20.9 lb, so a US ton is roughly 96 bars 20 ft long.
How do you calculate rebar weight?
Multiply the bar's cross-sectional area by its length and the density of steel. In US units, weight per foot is about the area in square inches times 3.40, so a #6 bar with 0.44 in² is about 1.50 lb/ft.
What is the density of steel?
Carbon steel is usually taken as 490 lb/ft³ or 7,850 kg/m³. Individual grades vary slightly, and stainless steels are a little heavier.
What is the d²/162 formula?
It gives the mass of a round steel bar in kg per metre when d is the diameter in millimetres. A 16 mm bar is 256 ÷ 162 = 1.58 kg/m.
How many feet of #4 rebar are in a ton?
A US ton (2,000 lb) of #4 rebar is about 2,994 linear feet, or roughly 150 bars 20 ft long.
Does this calculator size reinforcement?
No. It weighs the bars, plates and sections you enter. Bar size, spacing, cover and lap lengths come from the structural drawings or the applicable code.
Can I calculate the weight of a steel beam?
Yes, with the Known mass per length option. Enter the published weight per foot (a W8x31 weighs 31 lb/ft), then the length and quantity.
Do I need an account to download the result?
No. All calculations, local file processing and exports on this page are free, without an account.
Where are my inputs stored?
The tool keeps inputs in this browser tab. It does not upload them or create a cloud copy. Save or download anything you want to keep before leaving the page. Standard site analytics may operate independently of the tool.
Can I work in metric instead of imperial?
Yes. Use the Imperial / Metric switch above the inputs. Imperial (feet, inches, pounds, gallons) is the default; switching converts every dimensional field and result, and your choice is remembered across the free tools in this browser.
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