How do I calculate the weight per foot of a steel beam?

The weight per foot of any steel shape is calculated using: w (lb/ft) = A (in²) × 3.40, where A is the cross-sectional area in square inches. The factor 3.40 is derived from steel density (490 lb/ft³) × (1 ft/12 in)² × 12 in/ft = 490/144 × 12 = 3.403 lb/ft per in². For example, a W12x26 has A = 7.65 in², giving w = 7.65 × 3.40 = 26.0 lb/ft (matching the shape designation). The area can be obtained from the AISC Steel Construction Manual Part 1 tables. For shapes not in the manual: (a) Rectangular bar: A = width × thickness (in²). (b) Round bar: A = πd²/4, so w = d² × 2.676 (since π/4 × 3.40 = 2.670). (c) Pipe: A = π(OD² - ID²)/4. (d) Plate per foot of width: w = t (in) × 12 (in/ft) × 490/144 = t × 40.8 lb/ft per inch of width. For metric conversion: w (kg/m) = A (mm²) × 0.00785, derived from 7850 kg/m³ × (1 m/1000 mm)² × 1000 mm/m. The conversion between systems: 1 lb/ft = 1.488 kg/m.

What does the number after the x mean in a W-shape designation?

In the W-shape designation (e.g., W12x26), the number after the 'x' is the nominal weight per linear foot in pounds. W12x26 nominally weighs 26 pounds per foot. The first number is the nominal depth in inches (approximately 12 inches deep). The nominal weight derives from the cross-sectional area: weight = A (in²) × 3.40 lb/ft. Typical tolerances per ASTM A6/A6M allow ±2.5% variation from nominal weight. For example, a W14x90 (A = 26.5 in², nominal weight 90 lb/ft) may actually weigh between 87.75 and 92.25 lb/ft. The weight designation is critical for: (1) Dead load calculation — the self-weight of the beam is part of the total load the beam must support. (2) Erection planning — crane capacity must exceed the weight of the heaviest single piece. (3) Transportation — truck load limits (typically 40,000-80,000 lb gross) constrain how many pieces can ship together. (4) Cost estimation — steel is priced by weight (typically $0.50-1.50/lb fabricated, varying by complexity), so weight directly determines material cost. The lightest rolled W-shape is W4x13 (13 lb/ft), and common heavy shapes include W14x730 (730 lb/ft) and W36x925 (925 lb/ft), though the latter are built-up rather than rolled. For preliminary design, heavier W-shapes (higher lb/ft designation) within the same depth group have greater flexural and axial capacity.

How much does steel plate weigh per square foot?

Steel plate weighs 40.8 pounds per square foot per inch of thickness. This is the fundamental constant for all carbon steel plate weight calculations, derived from steel density 490 lb/ft³. Quick reference: 1/8 inch = 5.10 psf, 1/4 inch = 10.2 psf, 3/8 inch = 15.3 psf, 1/2 inch = 20.4 psf, 5/8 inch = 25.5 psf, 3/4 inch = 30.6 psf, 1 inch = 40.8 psf, 1-1/4 inch = 51.0 psf, 1-1/2 inch = 61.2 psf, 2 inch = 81.6 psf. For total plate weight: multiply plate psf by the plate area in square feet. A 5 ft × 10 ft, 1/2 inch plate: 20.4 psf × 50 ft² = 1,020 lb. A 4 ft × 8 ft, 3/4 inch plate: 30.6 psf × 32 ft² = 979.2 lb. In metric: 1 mm plate thickness weighs 7.85 kg/m² (7850 kg/m³ × 0.001 m). For example, 10 mm plate = 78.5 kg/m². A 1500 mm × 3000 mm (1.5 m × 3.0 m), 10 mm plate: 78.5 kg/m² × 4.5 m² = 353.3 kg. Plate weight is proportional to thickness — doubling the thickness exactly doubles the weight per square foot. For estimating total building steel plate weight, use 5-15% of the total steel tonnage as plate material, varying by connection type: simple shear connections use less plate (~5%), moment frames use more (~12-15% including stiffeners, continuity plates, and doubler plates).

How do I estimate the total steel weight of a building?

Building steel weight is estimated using pounds per square foot (psf) of floor area multipliers. Typical ranges: office buildings 6-10 psf, light industrial 5-8 psf, heavy industrial 8-15 psf, parking structures 8-12 psf, hospitals 10-15 psf, schools 6-10 psf. For a 5-story office building with 20,000 sf floor plates (100,000 sf total): estimated steel weight = 100,000 sf × 8 psf (mid-range) = 800,000 lb = 400 tons. These multipliers include all structural steel: beams, girders, columns, bracing, connections, and base plates. They do NOT include metal deck (2-4 psf additional), rebar (typically 3-6 psf of concrete area), or miscellaneous metals (stairs, railings, embeds). The multiplier varies with: framing system — moment frames use 10-20% more steel than braced frames or shear wall buildings due to drift-controlled design. Span length — longer spans (40+ ft) increase steel weight because deeper beams are needed for deflection control. Seismic design category — SDC D/E/F buildings use approximately 10-25% more steel due to capacity-design requirements, stronger connections, and drift limits. Gravity load — heavier live loads (storage, library stacks at 150 psf) drive steel weight higher than office live loads (50 psf + 20 psf partition). For more accurate takeoffs, the weight per foot of individual shapes is summed from a member schedule, adding 3-5% for connection material (bolts, plates, stiffeners).

How do I convert steel weight from lb/ft to kg/m?

Convert lb/ft to kg/m by multiplying by 1.488. This factor comes from: 1 lb = 0.453592 kg and 1 ft = 0.3048 m, so 1 lb/ft = 0.453592/0.3048 = 1.488 kg/m. Examples: W12x26 at 26 lb/ft = 38.7 kg/m. W14x90 at 90 lb/ft = 133.9 kg/m. W36x150 at 150 lb/ft = 223.2 kg/m. HSS 10x10x1/2 at 62.12 lb/ft = 92.4 kg/m. Reverse (kg/m to lb/ft): divide by 1.488, or multiply by 0.672. For density conversion: 490 lb/ft³ = 490 × 16.0185 = 7850 kg/m³ (where 16.0185 converts lb/ft³ to kg/m³). For cross-sectional area: 1 in² = 645.16 mm². The complete weight formula in metric: w (kg/m) = A (mm²) × 1E-6 × 7850 kg/m³ × 1 m/m = A × 0.00785. For quick mental conversion, 1 lb/ft ≈ 1.5 kg/m (10% high), and 1 kg/m ≈ 2/3 lb/ft. Common beam weights in both systems: W10x30 (US) = 30 lb/ft = 44.6 kg/m; UC 203x203x46 (UK) = 46 kg/m = 30.9 lb/ft. For crane selection, notes that 1 metric ton = 2204 lb, and 1 short ton (US) = 2000 lb. Always confirm which ton system your fabricator or crane company uses — mixing them causes a 10% error.

How do you calculate steel weight per foot?

Steel weight per foot = cross-sectional area (in²) × 3.4029 lb/ft per in². For example, a W12x26 beam has a cross-sectional area of 7.65 in², giving 7.65 × 3.4029 = 26.0 lb/ft. The weight per foot is embedded in the designation for standard W-shapes.

What does W12x26 mean?

W12x26 means a Wide Flange (W) shape approximately 12 inches deep, weighing 26 pounds per linear foot. The "26" after the "x" is always the weight per foot in plf. This is the standard AISC beam designation system.

What is the weight per foot of a 1-inch thick steel plate?

A 1-inch thick steel plate weighs approximately 40.8 lb/ft² (or 3.4 lb/ft² per 1/8 inch thickness). The formula is: weight = 0.2836 lb/in³ × thickness (in) × 144 in²/ft².

Steel Weight per Foot Chart — W, HSS, C, L Shapes

Knowing the weight per foot of structural steel shapes is essential for estimating, transportation planning, crane selection, and dead load calculations. This page provides weight tables for the most commonly used shapes and the formulas to calculate weight for any steel section.

Steel Density and Weight Formula

Density of steel: 490 lb/ft³ (7850 kg/m³)

Weight per foot formula:

w (lb/ft) = A (in²) × 3.40

where A is the cross-sectional area in square inches. The factor 3.40 comes from: 490 lb/ft³ × (1 ft/12 in)³ × 12 in/ft = 3.40 lb/ft per in².

For metric: w (kg/m) = A (mm²) × 7.85 × 10⁻⁶ × 1000 = A × 0.00785

W-Shape Weight Chart (AISC)

Shape	Weight (lb/ft)	Area (in²)	d (in)	bf (in)
W4x13	13	3.83	4.16	4.060
W6x15	15	4.43	5.99	5.990
W6x25	25	7.34	6.38	6.080
W8x18	18	5.26	8.14	5.250
W8x24	24	7.08	7.93	6.495
W8x31	31	9.12	8.00	8.000
W8x40	40	11.7	8.25	8.077
W10x22	22	6.49	10.17	5.750
W10x30	30	8.84	10.47	5.810
W10x45	45	13.3	10.10	8.022
W10x54	54	15.8	10.09	10.030
W12x26	26	7.65	12.22	6.490
W12x40	40	11.7	11.94	8.005
W12x50	50	14.6	12.19	8.715
W12x58	58	17.0	12.19	10.010
W12x65	65	19.1	12.12	12.000
W14x22	22	6.49	13.74	5.000
W14x30	30	8.85	13.84	6.730
W14x48	48	14.1	13.79	8.030
W14x61	61	17.9	13.89	9.995
W14x68	68	20.0	14.04	10.035
W14x82	82	24.1	14.31	10.130
W14x90	90	26.5	14.02	14.520
W16x36	36	10.6	15.86	6.985
W16x50	50	14.7	16.26	7.070
W18x40	40	11.8	17.90	6.015
W18x55	55	16.2	18.11	7.530
W18x76	76	22.3	18.21	11.035
W21x44	44	13.0	20.66	6.500
W21x57	57	16.7	21.06	6.555
W21x68	68	20.0	21.13	8.240
W24x55	55	16.2	23.57	7.005
W24x68	68	20.1	23.73	8.960
W24x84	84	24.7	24.10	9.020
W27x84	84	24.7	26.71	9.960
W27x102	102	30.0	27.29	10.010
W30x99	99	29.1	29.65	10.458
W30x124	124	36.5	30.17	10.510
W33x130	130	38.3	33.10	11.510
W36x150	150	44.2	36.74	12.000

HSS Weight Chart

Square HSS

Shape	Weight (lb/ft)	Area (in²)
HSS2x2x1/4	5.41	1.59
HSS3x3x3/16	7.07	2.08
HSS4x4x1/4	12.37	3.59
HSS5x5x3/8	22.37	6.59
HSS6x6x3/8	27.48	8.01
HSS6x6x1/2	35.24	10.37
HSS8x8x3/8	37.69	11.03
HSS8x8x1/2	49.16	14.46
HSS10x10x3/8	47.40	13.89
HSS10x10x1/2	62.12	18.27
HSS12x12x3/8	57.11	16.80
HSS12x12x1/2	75.08	22.08

Rectangular HSS

Shape	Weight (lb/ft)
HSS4x2x1/4	9.42
HSS6x4x3/8	22.37
HSS8x4x3/8	27.48
HSS8x6x3/8	33.76
HSS10x6x3/8	39.92
HSS12x6x1/2	75.08
HSS14x6x3/8	47.40
HSS16x8x1/2	89.68

C-Channel Weight Chart

Shape	Weight (lb/ft)	Area (in²)	d (in)	bf (in)
C3x4.1	4.1	1.21	3.00	1.410
C3x5	5.0	1.47	3.00	1.496
C3x6	6.0	1.76	3.00	1.596
C4x5.4	5.4	1.59	4.00	1.584
C4x7.25	7.25	2.13	4.00	1.721
C5x6.7	6.7	1.97	5.00	1.710
C5x9	9.0	2.64	5.00	1.885
C6x8.2	8.2	2.40	6.00	1.920
C6x10.5	10.5	3.07	6.00	2.034
C6x13	13.0	3.83	6.00	2.157
C7x9.8	9.8	2.87	7.00	2.090
C7x12.25	12.25	3.60	7.00	2.194
C7x14.75	14.75	4.33	7.00	2.299
C8x11.5	11.5	3.38	8.00	2.260
C8x13.8	13.8	4.04	8.00	2.343
C8x18.75	18.75	5.51	8.00	2.527
C9x13.4	13.4	3.94	9.00	2.433
C9x15	15.0	4.41	9.00	2.485
C9x20	20.0	5.88	9.00	2.648
C10x15.3	15.3	4.49	10.00	2.600
C10x20	20.0	5.88	10.00	2.739
C10x25	25.0	7.35	10.00	2.886
C12x20.7	20.7	6.09	12.00	2.942
C12x25	25.0	7.35	12.00	3.047
C12x30	30.0	8.82	12.00	3.170
C15x33.9	33.9	9.96	15.00	3.400
C15x40	40.0	11.80	15.00	3.520
C15x50	50.0	14.70	15.00	3.716

L-Angle Weight Chart

Shape	Weight (lb/ft)
L2x2x1/4	3.19
L2x2x3/8	4.70
L2-1/2x2-1/2x1/4	4.10
L2-1/2x2-1/2x3/8	6.00
L3x3x1/4	4.90
L3x3x3/8	7.20
L3x3x1/2	9.40
L3x2x1/4	4.10
L3x2x3/8	6.10
L4x4x1/4	6.60
L4x4x3/8	9.80
L4x4x1/2	12.80
L4x3x1/4	5.80
L4x3x3/8	8.50
L5x5x3/8	12.30
L5x5x1/2	16.20
L5x3-1/2x3/8	10.30
L6x4x3/8	11.70
L6x4x1/2	15.30
L6x6x3/8	14.90
L6x6x1/2	19.60
L8x8x1/2	26.40
L8x6x1/2	22.60
L8x4x1/2	19.60

Estimating Steel Weight — Quick Rules

Rule of Thumb: Weight per Foot

W-shapes: approximately 5-8% heavier than the designation suggests (W12x26 = 26 lb/ft)
HSS: multiply outside perimeter × wall thickness × 3.40
Plate: 40.8 psf per inch of thickness (or 20.4 lb/ft² per 1/2 inch)

Plate Weight per Square Foot

Thickness (in)	Weight (psf)
1/8	5.10
3/16	7.65
1/4	10.2
5/16	12.8
3/8	15.3
1/2	20.4
5/8	25.5
3/4	30.6
1	40.8
1-1/4	51.0
1-1/2	61.2
2	81.6

Estimating Total Building Steel Weight

Building Type	Steel Weight (psf of floor area)
Office building	6-10 psf
Light industrial	5-8 psf
Heavy industrial	8-15 psf
Parking structure	8-12 psf
Hospital	10-15 psf
School	6-10 psf

Metric Conversion

Unit	US Customary	Metric
Weight per foot	1 lb/ft	1.488 kg/m
Weight per foot	1 kg/m	0.672 lb/ft
Density	490 lb/ft³	7850 kg/m³
Area	1 in²	645.2 mm²

Frequently Asked Questions

How do I calculate the weight of a steel beam? Multiply the cross-sectional area (in²) by 3.40 to get lb/ft. For a W12x26 (A = 7.65 in²): 7.65 × 3.40 = 26.0 lb/ft.

What does the number after the x mean in a W-shape? It is the nominal weight per foot in pounds. W12x26 weighs approximately 26 pounds per linear foot.

How much does a 20 ft W18x55 beam weigh? 55 lb/ft × 20 ft = 1,100 lb (0.55 tons). Add approximately 2-3% for connections and details.

What is the weight of steel per square foot per inch of thickness? 40.8 psf per inch of thickness. So 1/4 inch plate weighs 10.2 psf, 1/2 inch plate weighs 20.4 psf.

How do I convert lb/ft to kg/m? Multiply by 1.488. Example: 26 lb/ft × 1.488 = 38.7 kg/m.

What does a typical steel building weigh? Office buildings: approximately 6-10 psf of floor area in structural steel. A 5-story, 20,000 sf floor plate building would contain roughly 600,000-1,000,000 lb (300-500 tons) of structural steel.

How do I estimate steel erection weight for crane selection?

Identify the heaviest single piece (typically the largest beam or girder)
Add 10% for rigging, connectors, and temporary bracing
Select a crane with rated capacity exceeding this weight at the required radius

Steel Weight Calculator — Interactive weight calculator
Steel Beam Sizes — W, HSS, C dimensions
Section Properties Database — Full searchable database
Plate Weight Calculator — Steel plate weight by thickness
Structural Steel Weights — Estimating guide

Disclaimer

This is a calculation tool, not a substitute for professional engineering certification. All results must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in construction, fabrication, or permit documents. The user is responsible for the accuracy of all inputs and the verification of all outputs.