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The cross-sectional area in square millimetres.
Metric bar sizes are named by diameter and tabulated by area: a 16 mm bar is 201 mm² if you compute it from the diameter and 200 mm² as the nominal figure the schedule uses. Use the tabulated nominal area rather than one you derive, because that is the number the design was checked against.
Area
0.31 in²
1 mm² = 1 ÷ 645.16 = 0.00155000 in². Exact by definition. Equal area is not equal development length; check anchorage separately.
- Square millimetres entered
- 0.31 in²
- Converted area
- 0.31 in²
- Square centimetres
- 0.31 in²
They open the calculator with your figures already in it
Square Millimetres to Square Inches Calculator: 0.31 in² — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- NIST SP 811, Appendix B — 1 mm² = 0.001550003 in²
- International yard and pound agreement, 1959 — the inch is exactly 25.4 mm
Inputs used
- Area (mm²)
- 200
Intermediate steps
- Square millimetres entered
- 0.31 in²
- Converted area
- 0.31 in²
- Square centimetres
- 0.31 in²
Confidence note: 1 mm² = 1 ÷ 645.16 = 0.00155000 in². Exact by definition. Equal area is not equal development length; check anchorage separately.
Add the equipment this sizes
This result is a specification — 0.31 in² — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-12 · v1.0.0
Regulatory standards & verification citations2
- NIST SP 811, Appendix B — 1 mm² = 0.001550003 in²
- International yard and pound agreement, 1959 — the inch is exactly 25.4 mm
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The check runs in this direction whenever the design is metric and the capacity table is not — a European or Canadian schedule being verified against ACI or AISC values written per square inch, or a metric section being substituted into a frame designed in imperial. Area is the right quantity to compare on, because it is what carries the load, but it is not the only quantity that has to match and the page says so rather than letting a clean conversion imply an equivalence it cannot support. The cm² row is there for the very common case of a section table quoted in square centimetres, which is the metric structural convention and a factor of a hundred away from the number this page expects.