Millimetres or inches? Kilometres or miles? This length converter translates between all eight common units — metric and imperial — using exact conversion factors, not rounded approximations. Pick your units, enter a value, and see the result plus the precise formula behind it.
Converted value
1,000.0000
Every conversion goes through metres, using exact factors:
value in metres = value × (metres per unit) → result = metres ÷ (metres per unit)
These imperial definitions were fixed by the 1959 international yard and pound agreement, so they're exact by definition — not measured approximations. Metric steps are pure powers of ten (1 km = 1,000 m).
Convert 1 mile to kilometres:
And 6 feet to centimetres: 6 × 0.3048 = 1.8288 m = 182.88 cm.
Converted value is shown to four decimal places — plenty for everyday use, from tailoring to road trips. The conversion used line shows the exact per-unit factor, so you can reuse it in a spreadsheet.
Need more precision (engineering, surveying)? The underlying factors are exact, so multiply the shown factor out to as many decimals as your work demands.
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Content last reviewed on 2026-10-06.