Methodology and sources
A reference site is only worth as much as the reader’s ability to check it. This page prints the formulas, cites the sources with what is taken from each, states the constants, describes the test that runs on every build, and lists the things the site does not claim.
The method
There is one identity behind every weight on this site, and one function that evaluates it:
Mass
m = A × 10⁻⁶ × ρ
A is the cross-sectional area in mm², ρ the density in kg/m³, m the mass in kg per metre of length. The 10⁻⁶ converts mm² to m².
Worked through with the default dimensions:
Circle: A = π/4 · d²Multiply by density: m = A × 10⁻⁶ × ρFor pipe: A = π/4 · (D² − d²) with d = D − 2tFor plate: m″ = t × ρ ÷ 1000, giving kg/m²Unit conversions applied only at output, never mid-calculation
- A
- Cross-sectional area from closed-form geometry — the only part that depends on the shape.
- ρ
- Density from the material specification. The only part that depends on the material.
- m
- Mass per unit length. Linear in density, and quadratic in a round bar’s diameter.
- Cross-sectional areas come from closed-form geometry, not from a table.
- Weights are computed as area × length × density, so they are exact for the dimensions and density you supply.
- Unit conversions use definitional constants only.
The calculators and the static tables call the same functions in the same module. There is no second implementation to drift out of step, which is why a calculator result and the table row printed beside it can never disagree — and why a fix to a formula lands on every page at once.
Area formulas, printed in full
Every area on this site comes from one of these. They are closed-form, so the accuracy of a result depends only on the dimensions entered — not on interpolating between tabulated rows.
| Section shape | Parameters | Formula | Expanded |
|---|---|---|---|
| Round Bar | d = diameter | A = π/4 · d² | A = π/4 × d², where d is the outside diameter |
| Square Bar | a = side | A = a² | A = a², where a is the side length |
| Hexagonal Bar | AF = across flats (af) | A = (√3/2) · AF² ≈ 0.8660 · AF² | A = (√3/2) × AF², where AF is the distance across flats (the wrench size), not across corners |
| Flat Bar | w = width, t = thickness | A = w · t | A = w × t, where w is width and t is thickness |
| Plate | w = width, t = thickness | A = w · t | A = w × t. For plate the useful output is mass per unit area: m″ = t × ρ |
| Round Tube | D = outside diameter, t = wall thickness | A = π/4 · (D² − d²), d = D − 2t | A = π/4 × (D² − d²), where D is the outside diameter, d the inside diameter, and d = D − 2t for wall thickness t |
| Square Tube | a = side, t = wall thickness | A = a² − (a − 2t)² | A = a² − (a − 2t)², which expands to A = 4t(a − t) |
| Rectangular Tube | a = depth, b = width, t = wall thickness | A = a·b − (a − 2t)(b − 2t) | A = a·b − (a − 2t)(b − 2t), which expands to A = 2t(a + b) − 4t² |
| Angle (L Section) | a = leg a, b = leg b, t = thickness | A = t · (a + b − t) | A = t × (a + b − t), where a and b are the two leg lengths and t the thickness. Equal-leg angles set a = b, giving A = t(2a − t) |
| Channel (U Section) | h = depth, b = flange width, t_w = web thickness, t_f = flange thickness | A = 2·b·t_f + (h − 2·t_f)·t_w | A = 2 × b × t_f + (h − 2 × t_f) × t_w, where h is the overall depth, b the flange width, t_f the flange thickness and t_w the web thickness |
Dimensions are in millimetres and areas in square millimetres throughout. Each formula is printed here exactly as it appears in the calculator and in the derivation block on the relevant pages.
Sources
What we take from each source, stated precisely — because "based on ASTM" is not a citation. Note in particular what is not taken: no standard’s text, notes or commentary is reproduced anywhere on this site.
| Key | Citation | Used for |
|---|---|---|
| asme-b36.10m | ASME B36.10M — Welded and Seamless Wrought Steel Pipe (dimensional tables). | Outside diameters and wall thicknesses for schedules 10, 20, 30, 40/STD, 60, 80/XS, 100, 120, 140, 160 and XXS from NPS 1/8 to NPS 36. |
| asme-b36.19m (print) | ASME B36.19M — Stainless Steel Pipe (dimensional tables). | Outside diameters and the Schedule 5S, 10S, 40S and 80S wall thicknesses used for stainless pipe. |
| astm-density (print) | ASTM material specifications for each grade named in the material entry (A36, A240/A276, B209/B211/B221, B152/B16/B505, B265/B348, A48, B29, D1784, D3350). | Nominal densities. Each material entry states the specification it represents. |
| iso-4427 (print) | ISO 4427 / ASTM D3350 — polyethylene pipe compounds (PE 100 material classification). | HDPE density band for PE 100 black compound. |
| geometry (print) | Elementary plane geometry. The circle, polygon and hollow-section area formulas. | Every cross-sectional area. These are closed-form formulas, not tabulated data, which is why the calculators are exact for whatever dimensions you enter. |
| si-definitions (print) | BIPM / NIST definitional constants: international inch = 25.4 mm, foot = 0.3048 m, pound = 0.45359237 kg. | All unit conversion factors. They are exact definitions, not measurements. |
Citations are reproduced on each relevant page’s own source block, so a reader arriving from search never has to come here to find out where a figure came from.
Densities
One nominal density per material grade, drawn from the specification named in each entry. Weight scales exactly with density, so a 1 % density error is a 1 % weight error — which is why the choice of value matters more than its apparent precision suggests.
| Family | Materials | Density range kg/m³ | With >±1 % spread |
|---|---|---|---|
| Carbon steel | 1 | 7,850 – 7,850 | 0 |
| Stainless steel | 4 | 7,700 – 8,000 | 0 |
| Aluminium | 3 | 2,680 – 2,810 | 0 |
| Copper alloys | 3 | 8,500 – 8,940 | 2 |
| Other metals | 3 | 4,510 – 11,340 | 1 |
| Polymers | 2 | 960 – 1,400 | 2 |
The carbon steel baseline is 7,850 kg/m³ (0.2836 lb/in³). Every relative figure on the site is measured against it. Full detail, including the spread values, is on the density chart.
Where a family genuinely varies, the spread is recorded rather than averaged away — see the density chart . For a large casting or an extrusion the producer’s own figure should be used instead of any nominal value.
Units and constants
All arithmetic is done in millimetres, kilograms and metres, and imperial values are produced only at the edge. Nothing is converted mid-calculation, so rounding cannot accumulate. The constants are definitional rather than measured:
- 1 in = 25.4 mm exactly — the international inch, 1959
- 1 ft = 0.3048 m exactly
- 1 lb = 0.45359237 kg exactly — the international avoirdupois pound
- 1 kg/m = 0.671969 lb/ft — derived, not typed
- 1 kg/m³ = 0.000036127 lb/in³ — derived, not typed
Water capacity figures use a conventional density of 1,000 kg/m³, which is not the density of water at any particular temperature: real water is 998.2 kg/m³ at 20 °C and 958 kg/m³ at 100 °C. A hydrostatic test mass computed from 1,000 is therefore about 0.2 % high at room temperature and 4 % high at boiling.
Verification
Two independent checks run on every build, before and after the pages are generated. They are not advisory: either one failing fails the build, and a failed Cloudflare Pages build leaves the previous deployment serving.
Before the build — dataset baseline (scripts/test_data.mjs)
- 52 assertions, all passing. Published reference values are checked to within 0.3 %: 1 in round bar at 2.6729 lb/ft, 1 in plate at 40.8383 lb/ft², 1 in hex bar at 2.9472 lb/ft, and Schedule 40 pipe at NPS 1, 2, 4, 6, 8 and 24 against their published weights.
- Whole-table cross-check.All 305 tabulated size-and-schedule combinations are compared against the industry chart formula, with a maximum deviation of 0.1052 % (at NPS 24 Schedule 10). That 0.1 % is entirely the density difference described above, and its consistency across the table is the evidence that the dimensional data was transcribed correctly.
- Unit round-trips.9 conversions are checked to return to their input, with a worst absolute error of 9.09 × 10⁻¹³ — floating-point noise, i.e. exact.
- Invariants and identities.Geometry cross-checks (a square bar at side d is 27.3 % heavier than a round bar at diameter d, a hollow section is lighter than the solid it replaces), the derivation of the STD and XS walls from Schedule 40 and 80, and the page-count matrix.
After the build — output guard (scripts/verify_build.mjs)
- Every sitemap shard is non-empty and the total clears the page floor.
- Every URL in every sitemap resolves to a real file on disk.
- No page is smaller than a real reference page could be — an empty template renders HTML too.
- Named data-bearing pages are checked for the presence of rendered figures, so a generator that silently produced empty tables is caught rather than shipped.
- No unresolved editorial marker or numeric artefact from a failed calculation survived into the output.
The previous site on this domain failed in exactly this way: a generator whose upstream data dried up, which wrote an empty section over a working one and was not noticed for weeks. "Remember to check the output" is not a control, so the check is a build step that exits non-zero.
Versioning and corrections
- Dataset version
- 2026.09.1 — moves only when a number changes, never on a cosmetic rebuild.
- Dimensions last verified
- 2026-09-21 — the date the dimensional tables were last checked against their sources.
- Standard editions in use
- ASME B36.10M-2018 / ASME B36.19M-2018
- Data volume
- 7,696 computed metal-weight rows · 367 tabulated pipe size-and-schedule rows · 16 materials · 10 section shapes · 31 nominal pipe sizes · 17 schedules.
- Corrections
- Reported through the contact page page and issued with a version bump. A correction to a density or a dimension changes every affected page and every CSV, because they are generated from one source.
What this site does not claim
Stated plainly, because the alternative is a reader assuming more than the data supports:
- We are not a substitute for the standard. Purchase and design against the standard itself.
- Nominal density is not a mill certificate. Wrought material varies; cast material varies more.
- Weight is not a strength or pressure rating. Nothing here tells you whether a part is safe.
- Section-property tables for named structural shapes (UPN, IPE, HEA, AISC C/MC) belong to the mills and standards that publish them; the parametric series on this site is for estimating only.
This is an estimating and checking aid. It tells you what a part weighs and what its cross-section is. It does not tell you whether it is safe, and no weight figure can.
Frequently asked questions
Where do the numbers come from?
Three places, and each value on the site says which. Pipe outside diameters and wall thicknesses are the tabulated ASME B36.10M-2018 / ASME B36.19M-2018 dimensional values. Densities are nominal engineering values from the material specification named in each entry — ASTM A36 for carbon steel, A240/A276 for stainless, B209/B211/B221 for aluminium, and so on. Everything else — every area, weight, bore, volume and surface area — is computed here from closed-form geometry. No weight is copied from a published chart.
How is the data checked before it is published?
A test suite runs as the first step of every build and refuses to let the build continue if it fails. It checks 52 things: published weight values against their sources within 0.3 %, a whole-table cross-check of 305 pipe size and schedule combinations against the industry chart formula, unit conversion round-trips, geometry identities, and the page-count matrix. Separately, a post-build guard verifies that every sitemap URL has a real page, that no page is suspiciously small, and that the data-bearing pages actually contain rendered numbers.
Why do your figures differ from a printed chart in the last digit?
Density, almost always. Printed steel weight tables use a nominal density — commonly 0.2833 or 0.2836 lb/in³, i.e. about 7,844 or 7,850 kg/m³ — and then round the result. We compute from the material specification density and display more significant figures, which is why a carbon steel figure can differ in the fourth figure and a 304 stainless figure runs about 1.9 % heavier for identical geometry. The test suite asserts that our values stay within 0.3 % of every published chart value we can check, which is tight enough to catch a transcription error and loose enough to allow the density difference.
Can I rely on these numbers for design?
For estimating, yes. For design certification, no, and the distinction is not a formality. Weight is a mass property; whether a part is safe is a strength, fatigue and pressure question that this site does not address at all. Beyond that, nominal density is not a mill certificate, and pipe wall thickness carries a manufacturing tolerance we do not apply — an acceptable pipe can be thinner than nominal. Use these figures to size, estimate and check, then design and purchase against the standard and the mill data.
What happens when a value is wrong?
It gets corrected and the dataset version moves — currently 2026.09.1, reviewed 2026-09-21. Because every page, every calculator and every CSV is generated from the same modules, a single correction propagates everywhere at once; there is no second copy to forget. The sitemap’s lastmod is driven by the version rather than the build date, so a rebuild that changes nothing does not falsely tell a crawler something moved. Report anything suspicious through the contact page and include the dimensions and density you used.
Why are some densities given as a range and others as one number?
5 of the 16 materials have a nominal value tight enough to state flatly: the carbon and stainless steels, aluminium, copper, titanium and lead. Cast iron (±3 %), bearing bronze (±3 %), PVC (±3 %) and HDPE (±2 %) do not, because graphite content, casting chemistry and plasticiser content really do move them that much. The spread is shown on the density chart and on every affected material’s own pages.
Reference data and tools
Where these methods are applied.
- Metal weight overview — how the calculation works
- All 16 materials — densities and specifications
- All 10 sections — formulas and size series
- Density chart — lightest to heaviest
- Metal weight calculator — any size, any material
- Pipe overview — schedules, sizes and how weight is computed
- All pipe schedules — Sch 5S to XXS
- All nominal sizes — NPS 1/8 to NPS 36
- DN to NPS conversion — metric to imperial designations
- Pipe weight formula — worked derivation
- Pipe weight calculator — any OD and wall
- All calculators — metal weight and pipe weight
- Download the data — CSV, generated from the same source
- Cross-reference tables — DN / NPS / material equivalents
- Methodology and sources — where every number comes from
This page states the method; the test suite enforces it. Both run on every build — the baseline check first, the output guard last — and either failing stops the deployment.
- Elementary plane geometry. The circle, polygon and hollow-section area formulas.
- ASME B36.10M — Welded and Seamless Wrought Steel Pipe (dimensional tables).
- ASME B36.19M — Stainless Steel Pipe (dimensional tables).
- ASTM material specifications for each grade named in the material entry (A36, A240/A276, B209/B211/B221, B152/B16/B505, B265/B348, A48, B29, D1784, D3350).
- ISO 4427 / ASTM D3350 — polyethylene pipe compounds (PE 100 material classification).
- BIPM / NIST definitional constants: international inch = 25.4 mm, foot = 0.3048 m, pound = 0.45359237 kg.
Dataset version 2026.09.1 · dimensions last verified against source 2026-09-21. Found an error? Report it — corrections are issued with a version bump.