How many cm is 1 inch?
Exactly 2.54 cm. This is the internationally standardized definition.
Convert between length units instantly.
Convert between different length units easily
Base unit: Meter
Available units: 14 units
Convert length by multiplying by the exact conversion factor: 1 inch = 2.54 cm exactly; 1 foot = 30.48 cm; 1 mile = 1.609344 km; 1 yard = 0.9144 m.
Length conversion is a multiplication operation using internationally standardized conversion factors. Since 1959, the inch has been defined as exactly 2.54 centimeters by international agreement, making all derived conversions exact.
**Common conversion factors:**
• 1 inch = 2.54 cm (exact)
• 1 foot = 30.48 cm = 12 inches (exact)
• 1 yard = 0.9144 m = 3 feet (exact)
• 1 mile = 1.609344 km = 5,280 feet (exact)
• 1 centimeter = 10 mm
• 1 meter = 100 cm = 1,000 mm
• 1 kilometer = 1,000 m
• 1 nautical mile = 1.852 km (international)
**Systems:**
• **Metric (SI)**: mm, cm, m, km — used globally, especially in science
• **Imperial/US customary**: inches, feet, yards, miles — used primarily in the US, with partial use in UK
• **Astronomical**: light-years, astronomical units (AU), parsecs — for cosmic distances
The calculator converts between all common length units instantly as you type.
Concise answers for common searches — definitions, steps, and comparisons.
Exactly 2.54 cm. This is the internationally standardized definition.
Exactly 1.609344 km. Divide by 1.609344 (or multiply by 0.621371) to convert km to miles.
Enter any length value in the input field and select the unit you are converting from.
Choose the unit you want to convert to — or see all units at once in the multi-unit display.
Results update instantly. Copy any value with the copy button.
For construction or shipping specs, convert back to the original unit to confirm accuracy before ordering materials or printing labels.
Common real-world scenarios where this tool saves time.
Convert between inches and centimeters when ordering clothing, furniture, or electronics from different countries (US uses inches; most of the world uses cm).
US construction uses feet and inches; metric countries use meters and millimeters. Convert between systems when following international plans or ordering metric materials.
Convert between 5K (5 km = 3.107 miles), 10K (6.214 miles), half marathon (13.11 miles = 21.097 km), and marathon (26.22 miles = 42.195 km).
Physics equations require SI units (meters). Convert feet, inches, or miles to meters/km before applying formulas involving speed, acceleration, or energy.
Key conversion factors between common units.
| From | To | Multiply by |
|---|---|---|
| Inches | Centimeters | × 2.54 |
| Centimeters | Inches | × 0.3937 |
| Feet | Meters | × 0.3048 |
| Meters | Feet | × 3.2808 |
| Miles | Kilometers | × 1.60934 |
| Kilometers | Miles | × 0.62137 |
| Yards | Meters | × 0.9144 |
| Meters | Yards | × 1.09361 |
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Exactly 2.54 centimeters. This is the internationally agreed definition since 1959: 1 inch ≡ 2.54 cm (exact). Therefore 1 cm = 1/2.54 inches = 0.393701 inches.
5,280 feet in a mile. This comes from the ancient Roman 'mille passuum' (thousand paces of a Roman soldier), where each pace was 5 feet. Combined: 5,000 Roman feet was adjusted to 5,280 by Elizabeth I in 1593 to align with the 8-furlong mile.
Multiply by 0.621371. Exact factor: 1 km = 0.621371192... miles (since 1 mile = 1.609344 km exactly). Quick mental approximation: multiply by 0.6 or divide by 1.6. Example: 10 km × 0.621 = 6.21 miles.
Convert feet to inches first (multiply by 12), then multiply total inches by 2.54. Example: 5 feet 10 inches = (5 × 12) + 10 = 70 inches × 2.54 = 177.8 cm.
Exactly 0.9144 meters (since 1 yard = 36 inches = 36 × 0.0254 m). Equivalently, 1 meter = 1.0936 yards. The US and UK both use this exact definition.
A nautical mile is 1,852 meters (1.852 km = 1.15078 statute miles). It is defined as one minute of arc along a meridian of the Earth, making it convenient for navigation. One nautical mile per hour = 1 knot.
Very nearly the same but technically different. The international foot (1959) = 0.3048 m exactly. The US survey foot (used in land surveys until 2023) = 1200/3937 m ≈ 0.3048006 m. The difference is 2 parts per million — meaningful only in geodesy and large-scale land surveying.
Length values you enter are converted locally in your browser—they are not uploaded to EverydayTools servers.
Minor floating-point rounding may appear for very large numbers or repeating decimals.
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Reviewed on 2026-06-08.