Type a value in the Square Centimetre (cm²) field and the equivalent in Square Inch (in²) appears instantly to the right. The math uses the exact formula shown above — no rounding errors, no approximations beyond standard floating-point precision. Use the swap button to flip the units and see the inverse conversion.

Square Centimetre. One ten-thousandth of a square metre. Common for small surface areas.

Square Inch. About 6.45 square centimetres. Used for screen sizes and small surface areas.

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No submit button — the result updates as you type. Math runs entirely in your browser, so it’s as fast as your device.

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🎯 Accurate conversions

Conversion factors come from the official standard (NIST, BIPM, ISO definitions where applicable). Values are precise to standard floating-point limits.

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How it works — the formula

Area scales as length squared.
For any length scale s (metres per unit), area scale = s².
1 ft² = 0.3048² m² = 0.09290304 m² exactly
1 acre = 4,046.8564224 m² exactly (= 1 chain × 1 furlong)

Area is a derived unit — the square of length — so any area conversion factor is the square of the corresponding length factor. The acre (4,046.8564224 m²) and hectare (10,000 m² exactly) are both standardized; one acre is also exactly 43,560 ft². Square metre is the SI derived unit.

Sources: NIST SP 811 §B.8 — Conversion factors for area · BIPM — SI brochure, derived units (square metre) · USDA NRCS — National Engineering Handbook (acre, square chain definitions)

Worked examples

Example 1

Imperial → metric

Inputs:: 1,500 ft² = ? m²
Output:: 1,500 × 0.09290304 ≈ 139.355 m²

Example 2

Acre to hectare

Inputs:: 5 acres = ? ha
Output:: 5 × 4,046.8564224 / 10,000 ≈ 2.0234 ha

Example 3

Square verification

Inputs:: (1 ft)² in m²
Output:: (0.3048 m)² = 0.0929 m² — squaring confirms the area scale

Limitations

Land-survey areas may use "US survey foot" rather than international foot — the difference is ~4 ppm, deprecated as of 2023.
Surface area on a curved manifold (sphere, ellipsoid) requires intrinsic geometry, not the flat conversion factor.
Floor-area definitions (gross vs net vs rentable) are governed by BOMA / IPMS standards, not unit conversion.
Pixel-area (digital images) is not a physical area unit — px² depend on display DPI.

Area conversions are exact rational arithmetic for SI ↔ US-customary; trailing-digit differences come from binary floating-point only.

Frequently asked

What is the formula for converting Square Centimetre to Square Inch?+

The formula is: 1 cm² = 0.155 in². Type any value into the calculator above and the result appears instantly.

How do I convert Square Inch back to Square Centimetre?+

Click the swap button (⇄) above to go to the Square Inch → Square Centimetre converter, or use the inverse formula derived from the one shown.

How accurate is the conversion?+

Conversion factors used here are exact rational values from NIST SP 811 and the BIPM SI brochure (e.g. 1 ft = 0.3048 m exactly, 1 lb = 0.45359237 kg exactly). Trailing-digit differences vs hand calculation come only from binary floating-point representation, never from the conversion factor itself.

Where do these conversion factors come from?+

Length and mass factors come from the 1959 international yard-and-pound agreement; SI base units (metre, kilogram, second, kelvin) come from the 2019 BIPM redefinition; energy and pressure factors are NIST SP 811 reference values. Each editorial section above lists the specific source for that category.

Can I copy the conversion factor for use elsewhere?+

Yes. The factor in the formula above is the exact rational value used internally; copying it into Excel or another tool reproduces the result to floating-point precision.

Related area tools

m² → ft² ft² → m² ha → ac ac → ha km² → mi² mi² → km²