Length
converter
Metric on one side, imperial on the other, pick your units, type a value, done. Millimeters to miles and everything between, using the exact defined factors.
Prefer a physical calculator?
A few solid picks. As an Amazon Associate, Calculate.to earns from qualifying purchases, at no extra cost to you.
OSALO Desktop Calculator
Extra-large 12-digit LCD, giant buttons, solar + battery, the classic office desk workhorse.
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Helix Oxford Scientific
240-function scientific calculator for KS3–KS4 maths, with hard cover. Exam-friendly, plastic-free packaging.
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Casio fx-83GTCW+
The UK classroom-standard scientific calculator (also in pink), allowed in most UK exams.
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ROATEE Construction Calc
Feet-inch-fraction engineering calculator for carpenters, framers and contractors on site.
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One base unit, exact bridges
Every conversion routes through the meter. Metric units are clean powers of ten; the imperial bridge has been exactly defined since 1959: one inch is precisely 2.54 cm, which fixes the foot (0.3048 m), yard (0.9144 m) and mile (1,609.344 m) with zero rounding.
1 mi = 1.609344 km · 1 km ≈ 0.6214 mi
Quick mental swaps
Kilometers to miles: multiply by 0.6 (or take five-eighths). Meters to feet: multiply by 3.3. Centimeters to inches: divide by 2.5. All within a couple percent, good enough for conversation, while the tool above stays exact. For area jobs like flooring, the square footage calculator works in the units builders quote.
Length FAQ
Exactly 2.54, defined by international agreement in 1959, not measured. Every imperial length conversion derives from it.
Divide by 1.609344, or mentally multiply by 0.6: a 10 km run is about 6.2 miles.
About 3.281 feet. Going the other way, a foot is exactly 0.3048 meters.
Because they're exact definitions, not measurements, 1 mile is precisely 1,609.344 m. The tool uses the full exact factor so no error accumulates.