How this calculator works
Pick a from-unit and a to-unit and type a value; the conversion and the exact factor for that pair appear instantly. Because every unit is defined in meters, any pair converts through a single exact ratio — there is no rounding chain to accumulate error.
These are the international definitions used in engineering and trade. (US land surveying used a marginally different 'survey foot' until it was retired at the end of 2022; the difference is 2 parts per million and irrelevant outside legacy survey data.)
How it converts
result = value × (meters per from-unit) ÷ (meters per to-unit)Exact anchors: 1 in = 0.0254 m · 1 ft = 0.3048 m · 1 yd = 0.9144 m · 1 mi = 1,609.344 mWorked example: 100 cm to inches
- 100 cm = 1 meter.
- 1 m ÷ 0.0254 m/in = 39.3701 inches.
- So 100 cm ≈ 39.37 in — and exactly 5,000⁄127 as a fraction, since the definition is exact.
Frequently asked questions
Is 1 inch exactly 2.54 cm, or approximately?
Exactly, by definition, since the 1959 international yard and pound agreement. Before that, the US and UK inches differed by a few parts per million.
How many feet are in a mile?
5,280 feet, which is 1,760 yards. In metric terms that is exactly 1,609.344 meters.
What is the quick mental trick for km and miles?
Multiply miles by 1.6 for kilometers, or use the Fibonacci coincidence: 3 mi ≈ 5 km, 5 mi ≈ 8 km, 8 mi ≈ 13 km — accurate to within about 1%.
Why do my results show more decimals than my ruler can measure?
The converter reports the mathematically exact value. Round to the precision your measurement actually supports — converting a value can never make it more precise than it was measured.
How many centimeters are in a meter?
Exactly 100. The metric prefix 'centi' means one-hundredth, so 100 cm always equals 1 m — the same relationship this page's own worked example starts from (100 cm = 1 meter) before converting to inches.