Using This Calculator With Metric Measurements

This calculator's input fields are labeled in feet and inches, but the actual math underneath is unit-agnostic — it's all ratios and area, so metric measurements convert cleanly with no loss of accuracy. Here's exactly how to do it.

The conversion factors you need

• Room dimensions (cm or m to feet): divide centimeters by 30.48, or multiply meters by 3.281, to get feet for the room length/width fields.
• Tile dimensions (mm to inches): divide millimeters by 25.4 to get inches for the tile length/width fields. A common metric tile size, 300mm × 300mm, converts to 11.81" × 11.81".
• Grout width (mm to inches): same conversion — a 3mm grout joint is 0.118", which rounds cleanly enough to enter as 0.12".

Worked example: a 4m × 3.5m room, 600mm × 600mm tile

Room: 4m = 13.12 ft, 3.5m = 11.48 ft. Tile: 600mm = 23.62". Grout: 3mm = 0.118". Entering 13.12 / 11.48 for room length/width, 23.62 / 23.62 for tile length/width, and 0.118 for grout gives the same effective-tile-footprint math the calculator always runs — (23.62+0.118)/12 × (23.62+0.118)/12 ≈ 1.978 sq ft per tile — and the room area, tiles needed, and grout length results that follow are exactly as accurate as if the fields were metric-native.

Why there's no accuracy loss

Every formula this calculator runs — effective tile footprint, coverage tiles, waste-adjusted tiles to buy, grout line length — is built from ratios of the same measurement system you enter, not from any fixed real-world constant that would need unit-specific calibration. Converting cm/mm to feet/inches before entering values, then (if needed) converting the result's square-footage or grout-length figures back to square meters or meters afterward, introduces no more rounding error than the inputs you already measured to.

Converting results back to metric

• Square feet to square meters: multiply by 0.0929.
• Grout length in feet to meters: multiply by 0.3048.

Tile and box counts need no conversion at all — "14 tiles" and "2 boxes" are the same regardless of which unit system you measured the room in.

Common metric tile sizes for quick reference

Metric size	Imperial equivalent (to enter)
200mm × 200mm	7.87" × 7.87"
300mm × 300mm	11.81" × 11.81"
300mm × 600mm	11.81" × 23.62"
600mm × 600mm	23.62" × 23.62"
600mm × 1200mm	23.62" × 47.24"

FAQ

Will rounding my metric-to-imperial conversion cause a meaningfully wrong tile count?

No — the calculator already rounds up to whole tiles at the final step, so a conversion precise to two decimal places introduces far less error than that final rounding step itself.

Is there a metric version of this calculator?

Not currently — the fields are imperial, but as shown above the underlying math works identically with converted metric inputs.

Does the Australia-specific page use metric or imperial?

See the Australia tile sizing page — it works through common AU metric tile sizes and m² room areas using the same conversion approach shown here.

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