How do I convert imperial measurements to metric for a floor plan?

Multiply each linear dimension by 25.4 to go from inches to millimetres, or by 0.3048 to go from feet to metres. Recompute area from the converted dimensions instead of converting square feet directly, so rounding does not compound across the drawing set. Arch Convert handles length, area, and volume in sync.

What are the most common imperial to metric conversion factors used by architects?

1 inch equals 25.4 mm exactly. 1 foot equals 304.8 mm or 0.3048 m. 1 square foot equals 0.0929 square metres. 1 acre equals 4046.86 square metres or 0.4047 hectares. 1 cubic foot equals 0.0283 cubic metres. These are the values Arch Convert uses internally.

Why do I need a unit converter when I can just use Google?

Google handles single conversions but not architectural workflows. You often need feet plus fractional inches (5' 3 1/2"), several units side by side, or arithmetic on mixed units. Arch Convert keeps every unit visible, supports fractions and expressions like 12 1/2 + 3, and switches between length, area, and volume without losing your value.

Imperial to Metric Converter for Architects

1 foot equals 304.8 mm exactly and 1 acre equals 4046.86 m². Use the converter to swap between feet, inches, square feet, square metres, acres, and hectares without rounding errors.

Open the imperial to metric calculator →

Worked example

A 24'-0" x 36'-0" room is 7.3152 m x 10.9728 m, which works out to about 80.26 m² (864 sq ft x 0.0929). Converting each dimension first and then multiplying gives a more accurate area than converting square feet straight across.

Conversion reference

Imperial	Metric
1 foot	304.8 mm
1 inch	25.4 mm
1 square foot	0.0929 m²
1 acre	4046.86 m² (0.4047 ha)
1 hectare	10,000 m² (2.4711 acres)

Arch Convert covers the units architects and contractors actually move between every day: feet and inches, fractional inches, decimal inches, millimetres, metres for linear work, plus square feet, square metres, acres, and hectares for site areas. Switch tabs in the calculator to jump between length, area, and volume.

Frequently asked

How do I convert imperial measurements to metric for a floor plan?: Multiply each linear dimension by 25.4 to go from inches to millimetres, or by 0.3048 to go from feet to metres. Recompute area from the converted dimensions instead of converting square feet directly, so rounding does not compound across the drawing set. Arch Convert handles length, area, and volume in sync.
What are the most common imperial to metric conversion factors used by architects?: 1 inch equals 25.4 mm exactly. 1 foot equals 304.8 mm or 0.3048 m. 1 square foot equals 0.0929 square metres. 1 acre equals 4046.86 square metres or 0.4047 hectares. 1 cubic foot equals 0.0283 cubic metres. These are the values Arch Convert uses internally.
Why do I need a unit converter when I can just use Google?: Google handles single conversions but not architectural workflows. You often need feet plus fractional inches (5' 3 1/2"), several units side by side, or arithmetic on mixed units. Arch Convert keeps every unit visible, supports fractions and expressions like 12 1/2 + 3, and switches between length, area, and volume without losing your value.