Length converter
Length converter
One length in millimetres, centimetres, metres, inches, feet and yards at once, so a measurement taken in one unit can be read, ordered and checked in another.
How this is calculated
Every unit is defined exactly against the metre: a millimetre is 0.001 m, a centimetre 0.01 m, an inch 0.0254 m, a foot 0.3048 m and a yard 0.9144 m. The value is multiplied into metres once and divided back out into each unit, so no conversion passes through a rounded intermediate figure. The feet-and-inches line takes the whole feet and prints the remainder to two decimal places.
- These are the international definitions, which is what a drawing, a specification sheet and a tape measure in India use. Older local feet — the survey foot used in some revenue records — differ by a few parts per million and are not what this page converts. If a document says which foot it uses, follow that document.
- A conversion this exact does not make the original measurement exact. A wall measured to the nearest inch is worth an inch, however many decimal places the metre figure carries; read the converted number back at the precision of the tape, not of the arithmetic.
A tape is marked in feet and inches, a drawing is dimensioned in millimetres, and the order form asks for metres. This page holds the three in one place and converts between them with the exact definitions rather than a rounded rule of thumb.
Every unit here is an exact multiple of the metre
The inch is defined as 25.4 millimetres, the foot as twelve inches and the yard as three feet, so all three follow from the metre to the last decimal place. The conversion multiplies your figure into metres once and divides back out into each unit, which means no answer passes through a rounded intermediate value and the millimetre and the yard figures cannot drift apart.
The feet-and-inches line is a reading aid, not a more accurate answer. It takes the whole feet and prints the remainder in inches to two decimal places, and it rolls 11.995 inches up to the next foot so a whole number of feet never appears as 11 ft 12 in. Read it at the precision of the tape that took the measurement: a wall measured to the nearest inch is worth an inch however many decimals the metre figure carries.
Questions readers ask
Why is a foot exactly 0.3048 m?
Because the international yard and pound agreement defined the yard as 0.9144 m exactly and the foot as one third of it. The figure is a definition agreed between countries, not a measurement of a particular object, which is why it can be used to the last decimal place.
Does this convert the survey foot in old revenue records?
No. Some historical survey systems used a foot that differs from the international foot by a few parts per million, and a few records still use it. The difference is small but it is not zero, so if a document names the foot it used, apply that document’s conversion instead of this one.
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