Metal Weight Calculator
Calculate the weight of bar, tube, plate or box stock in steel, aluminium, brass, copper and more. Instant weight in kg and cost estimate.
Metal Weight Calculator: How Much Does Your Metal Stock Weigh?
Before you order bar, tube or plate stock, or before a delivery truck, crane or courier quotes you a price, you usually need one number first: how much does it actually weigh? This metal weight calculator works out that number from three things — the shape of the stock (round bar, round tube, or rectangular plate/box), its dimensions, and the metal it's made from — then converts the result into a per-piece weight, a total weight for however many pieces you're ordering, and a material cost estimate.
This is the general, multi-metal version of the calculator: it covers 13 common metals and alloys (aluminium, magnesium, steel, brass, bronze, copper, zinc, lead, nickel, titanium, silver, gold and platinum) with a standard reference density for each, plus a custom-density option for anything not on the list. If you work exclusively in one metal and want grade-specific presets — different steel or aluminium alloys, for instance — the dedicated steel weight and aluminium weight calculators go deeper on just that metal; this tool is built for the more common case of comparing metals or working across mixed-material stock.
How to Use the Metal Weight Calculator
- Choose the shape: round bar (a solid rod), round tube (a hollow pipe), or rectangular prism (plate, sheet or box stock).
- For a round bar or tube, enter the outer diameter and choose its unit (mm, cm, m, in or ft).
- For a round tube, also enter the inner diameter — the hole through the middle — so the calculator can subtract the hollow core from the solid volume.
- For a rectangular prism, enter the width and thickness (with units) instead of a diameter.
- Enter the length of the stock and choose its unit.
- Set the quantity — how many identical pieces you are weighing.
- Choose the metal or alloy from the density preset list, or switch to a custom density (kg/m³) for a specific grade or material not listed.
- Choose your output mass unit (kg, g, lb or oz).
- Read off the weight per piece, the total weight for the full quantity, and an estimated material cost, editing the price per kg to match your supplier.
The Math Behind the Calculation
The core formula is the same for every shape and metal: total weight = volume × density × quantity. Only the volume formula changes depending on the shape you pick. A round bar is a solid cylinder, so its volume is V = π × r² × L, where r is the radius (half the diameter) and L is the length. A round tube is a hollow cylinder, so its volume is the outer cylinder minus the inner one: V = π × (R² − r²) × L, using the outer radius R and inner radius r. A rectangular prism — plate, sheet or box stock — is simply V = L × W × T (length × width × thickness).
Once the volume is found (always converted to cubic metres internally, regardless of which units you entered), it is multiplied by the density of the chosen metal in kg per cubic metre to get the weight of a single piece, then multiplied again by the quantity to get the total weight for the order.
Worked example: a solid steel round bar, 20 mm diameter, 6 m long, quantity 10, using steel's standard reference density of 7,860 kg/m³. Radius = 10 mm = 0.01 m. Volume per bar = π × (0.01)² × 6 = π × 0.0006 ≈ 0.0018850 m³. Weight per bar = 0.0018850 × 7,860 ≈ 14.82 kg. For 10 bars, total weight = 14.82 × 10 ≈ 148.2 kg.
Standard Reference Densities by Metal (kg/m³)
- Aluminium (average): 2,700
- Magnesium: 1,780
- Titanium: 4,506
- Zinc: 7,140
- Steel: 7,860
- Brass: 8,500
- Nickel: 8,900
- Bronze: 8,800
- Copper: 8,960
- Silver: 10,490
- Lead: 11,340
- Gold: 19,300
- Platinum: 21,500
- Source: standard engineering materials-density reference figures used across metalworking and fabrication contexts. These are average figures for the base metal — always confirm the exact density of your specific alloy or grade against a materials standard (e.g., ASTM, EN, JIS) for engineering-critical or high-value work.
UK Steel Standards
- General structural and engineering steel bar in the UK is specified under BS EN 10025 (the British-adopted version of EN 10025), with grades such as S275 and S355 the most common for fabrication and general engineering use.
- Round bar is typically stocked in 3 m and 6 m lengths and sold by weight — source: BS EN 10025-2 and standard UK steel-stockholder practice.
Pro Tips and Common Mistakes
At a typical trade price of around £2.20 per kg for mild steel round bar stock, the worked example above (a 20 mm bar, 6 m long, quantity 10, weighing roughly 148.2 kg) would cost about £326 in raw material — cutting to length, delivery and any surface finishing are additional.
- Enter the full diameter, not the radius — this is the single most common input mistake, and it roughly doubles (or, since volume scales with radius squared, can badly distort) the computed weight.
- For a round tube, the wall thickness is implied by the gap between outer and inner diameter — it is (outer diameter − inner diameter) ÷ 2, not the inner diameter itself.
- Switch to a custom density whenever you know the certified figure for your exact alloy or grade (e.g., a specific stainless steel or aluminium series) — the presets here are general reference averages, not grade-specific certificates.
- This calculator assumes solid, uniform-density metal throughout — it does not account for coatings, plating, surface treatments, or voids.
- Weight scales linearly with quantity, so a small dimension error on a single piece compounds across a large order — double-check your inputs before ordering a big batch or booking freight.
- If you work almost exclusively with one metal and want alloy-specific presets, the dedicated steel weight or aluminium weight calculators are built specifically around those metals.
