Random lengths are commonly 5.8 m or 6 m
Theoretical weight
— kg
per piece
Outside diameter D—
Wall thickness S—
Dimension—
Quantity—
Total—
—
Theoretical figure for planning only. We invoice against the actual weight on the
EN 10204 3.1 certificate.
Two reasons the figure above will not match your packing list.
1 · Mill tolerance. Seamless pipe wall thickness commonly carries ±12.5%, which moves the weight by roughly the same proportion.
2 · Forming allowance on fittings. A butt-weld elbow is not a pure torus — extra material is left at the extrados so the wall still meets minimum thickness after forming. Checked against published catalogue weights from 4" to 24", real long-radius elbows run about 4–7% heavier than the theoretical figure, consistently across the size range. Pipe, by contrast, matches its published mass almost exactly.
Use this for freight planning and budget estimates. For invoicing, the number that counts is the actual weight on the EN 10204 3.1 certificate.
1 · Mill tolerance. Seamless pipe wall thickness commonly carries ±12.5%, which moves the weight by roughly the same proportion.
2 · Forming allowance on fittings. A butt-weld elbow is not a pure torus — extra material is left at the extrados so the wall still meets minimum thickness after forming. Checked against published catalogue weights from 4" to 24", real long-radius elbows run about 4–7% heavier than the theoretical figure, consistently across the size range. Pipe, by contrast, matches its published mass almost exactly.
Use this for freight planning and budget estimates. For invoicing, the number that counts is the actual weight on the EN 10204 3.1 certificate.
What the calculator uses
Everything here is published openly. Nothing is a proprietary black box — the substituted formula is shown with every result so you can check it by hand.
| Item | Formula | Where the dimension comes from |
|---|---|---|
| Steel pipe | W = 0.02466 × S × (D − S) | kg per metre. D and S from ASME B36.10M |
| 90° elbow | W = 0.0387 × S × (D − S) × R / 1000 | R = centre-to-end. LR = 1.5 × NPS, SR = 1.0 × NPS per ASME B16.9 |
| 45° elbow | above × 0.5 | Half the arc of a 90° |
| 180° return | above × 2 | Twice the arc of a 90° |
| Equal tee | W ≈ 0.02466 × S × (D − S) × (2C + M) / 1000 | C and M are tabulated in ASME B16.9 — enter from your drawing |
| Cross | W ≈ 0.02466 × S × (D − S) × (2C + 2M) / 1000 | As above |
| Reducer | W ≈ 0.02466 × S × ((D₁+D₂)/2 − S) × H / 1000 | H = end-to-end length, tabulated in ASME B16.9 |
| Cap | W ≈ 0.02466 × S × (D − S) × H / 1000 | H = cap height, tabulated in ASME B16.9 |
| Flange, valve | no closed formula | Masses tabulated in ASME B16.5 / B16.47 / EN 1092-1 — ask us |
Constant 0.02466 = π/4 × 7.85 ÷ 1000, i.e. carbon steel density in kg per mm² per metre. Stainless grades are scaled by density ratio: 304 ×1.01, 316L ×1.02.
Questions this tool gets asked
Is theoretical weight the same as the invoiced weight?
No. Theoretical weight is a planning figure from nominal dimensions at 7.85 kg/dm³.
Actual weight moves with mill tolerance on wall thickness — commonly ±12.5% on seamless.
We invoice against the actual weight on the EN 10204 3.1 certificate, so the two will differ.
Where do the OD and wall thickness values come from?
They are the nominal values defined in ASME B36.10M. Choosing a size and schedule
looks them up so you do not have to work from the table. Where a schedule is not defined for a
given size, it is simply not offered in the dropdown rather than being interpolated.
What bend radius is used for elbows?
Long radius uses centre-to-end = 1.5 × NPS and short radius 1.0 × NPS, as defined in
ASME B16.9. The substituted formula is printed with every result so the figure can be verified.
Why do tees, reducers and caps ask me for a dimension?
Because unlike elbows they are not a simple multiple of the nominal size — C, M and H
are tabulated values in ASME B16.9. Rather than guess them, the calculator applies the formula to
the dimension you enter from your drawing or from the standard. If you would like us to fill them
in, send the size list and we will return a weighed quotation.
Can I calculate flange or valve weight?
Not from a formula — there isn't one. Flange and valve masses are tabulated by class
and facing in ASME B16.5, B16.47 and EN 1092-1. Send size, class and facing and the mass comes
back with the quotation.
Need the real number rather than the theoretical one?
Send a size list or a drawing. We return the weighed quotation with the governing standard, material grade and certification stated on it — and we take drawings as attachments directly on the inquiry form.
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