How this instrument works
Every bar shape reduces to the same underlying calculation once you have its cross-sectional area: weight equals area times length times density, times however many identical pieces you need. What differs between round, square, and rectangular bar is only how that cross-sectional area is found — π·d²/4 for a circle, side² for a square, and width × height for a rectangle — after which the rest of the arithmetic is identical for all three shapes.
This calculator is scoped to bar stock specifically — solid round, square, and rectangular cross-sections — and deliberately does not cover flat plate, which is a distinct calculation (length × width × thickness, with no separate cross-section-then-length step) better handled by a dedicated plate-weight tool. Bar and plate get quoted, stocked, and cut differently in practice, so keeping the two calculations separate avoids blurring what's really two different shapes of raw material.
The density used is 0.2836 lb per cubic inch, the standard reference value for mild and carbon steel (converted from 7,850 kg/m³) — a genuine physical material property, not a coverage rate or product assumption that varies by supplier the way many other defaults in this category do.
- Choose the bar shape: round, square, or rectangular.
- Enter the relevant cross-section dimension — diameter for round, side length for square, or width and height for rectangular.
- Enter the bar length, in inches, and the quantity of identical pieces.
- Read Cross-sectional area and Total weight in pounds — the combined weight of all pieces at that length.
Worked example — a 10-foot length of 1-inch round bar
A single piece of 1-inch-diameter round steel bar, 120 inches (10 feet) long, needs a weight for a shipping estimate. Cross-sectional area = π × 1² / 4 = 0.785398 sq in. Weight = 0.785398 × 120 × 0.2836 × 1 = 26.7287 lb for that one piece.
Compare that to two 20-foot lengths (240 in) of 1.5-inch square bar: area = 1.5² = 2.25 sq in per piece; weight per piece = 2.25 × 240 × 0.2836 = 153.144 lb, and for the full order of two pieces, total weight = 306.288 lb — illustrating how quickly a larger square cross-section and a longer run add up compared with a slender round bar.
Questions
How do you calculate the weight of a steel bar?
Find the cross-sectional area for the bar's shape (π·d²/4 for round, side² for square, width × height for rectangular), then multiply by the bar's length, steel's density, and the quantity of pieces. All three shapes share the same weight formula once the cross-sectional area is known — only the area formula changes by shape.
What's the difference between this and a steel plate weight calculator?
This calculator covers bar stock — round, square, and rectangular cross-sections stocked and cut by length — while a plate calculator covers flat sheet stock, found from length × width × thickness with no separate cross-section step. The two are genuinely different shapes of raw material, priced and ordered differently, so they're kept as separate tools rather than one calculator trying to cover both.
What steel density does this calculator assume?
0.2836 lb per cubic inch, the standard reference density for mild and carbon steel (converted from 7,850 kg/m³). This is a textbook physical property rather than a product-specific coverage rate, so it's fixed in the calculation rather than exposed as something to adjust for a particular supplier or grade.
How much does a 20-foot piece of square steel bar weigh?
It depends on the bar's side dimension, since weight scales with the square of that measurement. A 1.5-inch square bar, 240 inches (20 ft) long, weighs 1.5² × 240 × 0.2836 ≈ 153.1 lb; a 2-inch square bar of the same length weighs 2² × 240 × 0.2836 ≈ 272.3 lb. Enter your exact dimensions here rather than relying on a rule of thumb.
Can I calculate the weight of multiple identical bars at once?
Yes — enter the quantity of identical pieces alongside the shape, cross-section, and length, and the Total weight figure multiplies the per-piece weight by that count automatically. This is useful for pricing a full order rather than calculating one piece and multiplying by hand afterward.