Unit Converter

Convert between imperial/metric units and work with fractions.

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About the Unit Converter

This unit converter translates measurements between metric and imperial systems — length, area, volume, weight, and more — with support for fractional inches so shop measurements convert cleanly. It is the quick reference for anyone working from plans drawn in one system while using tools marked in another.

Converting between systems

Every conversion is a multiplication by a fixed factor. One inch is exactly 25.4 millimetres, one foot is 0.3048 metres, and one pound is 0.45359237 kilograms. The converter applies the correct factor for the measurement type and unit you choose, and can return fractional inches (to the nearest 1/16 or 1/32) rather than awkward decimals when converting back to imperial.

Because the factors are exact definitions rather than approximations, conversions are precise; the only rounding happens when you ask for a fractional result, which snaps to the nearest practical tape-measure marking.

When you need it

Plans and hardware increasingly mix systems: European hinges in millimetres, North American lumber in inches, fasteners in both. A converter removes the mental arithmetic and the risk of transposing a factor. It is especially handy for translating a metric drawing into the fractional inches your tape and rules are marked in, and vice versa.

Worked example

A plan calls for a 38 mm thick top, but your planer and tape read in inches.

Divide millimetres by 25.4: 38 ÷ 25.4 = 1.496 inches.
Round to the nearest sixteenth: 1.496 is very close to 1 1/2 (1.5).

38 mm is effectively 1 1/2 inches — a standard 8/4 dressed thickness.

Frequently asked questions

How many millimetres are in an inch?

Exactly 25.4 millimetres. This is a defined value, so an inch-to-millimetre conversion is exact rather than approximate.

Can the converter return fractions of an inch?

Yes. When converting to imperial it can express the result as a fraction (for example 1 1/2 in) rounded to the nearest sixteenth or thirty-second, which matches the markings on a tape measure.

Why do my converted measurements sometimes look slightly off?

Fractional inches are rounded to the nearest practical marking, so a metric value rarely lands exactly on a sixteenth. For joinery, work to the decimal value where precision matters and use the fraction as a cutting reference.