Length and size converters
Convert between metric and imperial lengths: centimeters, inches, feet, meters, millimeters, kilometers and miles. Instant results for shopping, travel, construction and everyday measurements.
Last updated: May 2026
Metric and imperial
Most length conversions come down to one job: a spec sheet, product listing or map distance is in the wrong unit system. These are the most-used converters.
Smaller units
Millimeters and fractional inches come up in manufacturing, 3D printing, machining and detailed product specs.
When you need a length converter
Length is the most common source of metric versus imperial confusion. A screen listed in inches, a piece of furniture in centimeters, a road sign in miles, a product spec in millimeters: each one forces a conversion the moment you try to compare prices or place an order.
The most practical rule is to pick one unit system and convert everything else into it before you start. Mixing systems halfway through a project, a build or a shopping comparison is where the costly mistakes happen.
Most everyday length factors are fixed by definition rather than measured, so they never drift: one inch is exactly 2.54 cm, one foot is 0.3048 m, and one mile is 1.609344 km. A conversion is therefore only as accurate as the number you start with, not the factor.
Length and distance conversion factors
| Conversion | Multiply by | Example |
|---|---|---|
| Inches to cm | 2.54 | 10 in = 25.4 cm |
| cm to inches | 0.3937 | 30 cm = 11.8 in |
| Feet to meters | 0.3048 | 6 ft = 1.83 m |
| Meters to feet | 3.2808 | 2 m = 6.56 ft |
| Miles to km | 1.6093 | 5 mi = 8.05 km |
| mm to inches | 0.03937 | 50 mm = 1.97 in |
Where each unit appears in practice
Different length units dominate in different contexts, and mixing them is where errors occur. The table below shows which unit a specification or measurement is likely to use for common tasks, so you know which converter to reach for.
| Context | Typical unit | Common conversion need |
|---|---|---|
| Screen size (TV, monitor, phone) | Inches (even in metric countries) | Inches to cm for fitting into furniture or a cabinet |
| Body height | Feet and inches (US, UK) or cm (EU) | Feet plus inches to cm for medical records or online shopping |
| Road distance / navigation | Miles (US, UK) or km (EU) | Km to miles for UK road signs; miles to km for European driving |
| Construction and DIY | Mm or cm (EU), inches (US) | Mm to inches for imported hardware; feet to metres for room dimensions |
| Clothing measurements | Inches (US) or cm (EU) | Waist/chest/inseam in inches to cm for international sizing charts |
| 3D printing tolerances | Millimetres (always) | Mm to inches for US-spec parts or inch-based designs |
Frequently Asked Questions
How do I convert centimeters to inches by hand?
Divide the number of centimeters by 2.54, because one inch is defined as exactly 2.54 cm. For example, 30 cm divided by 2.54 is about 11.8 inches. To go the other way, multiply inches by 2.54.
Which countries still use imperial length units?
The United States uses inches, feet and miles for most everyday measurements. The United Kingdom and Canada are mixed: metric officially, but road distances stay in miles and body height in feet and inches. Most other countries are fully metric.
Why is a 55-inch TV not 55 inches wide?
Screen size is measured along the diagonal, not the width. For a standard 16:9 television the width is roughly the diagonal times 0.87, so a 55-inch screen is about 48 inches (122 cm) wide. Check width and height separately when fitting a screen into a space.
Are these conversions exact or rounded?
The underlying factors are exact by definition (1 inch = 2.54 cm, 1 mile = 1.609344 km). Results shown are rounded to a sensible number of decimals for readability, so for engineering work keep more decimals than the display shows.
What is the quickest way to estimate kilometers to miles in my head?
Multiply kilometers by 0.62, or use the rough trick of multiplying by 5 and dividing by 8. For example, 80 km times 5 is 400, divided by 8 is 50 miles (the exact figure is 49.7).
How do I convert feet and inches to centimetres?
Convert feet to inches first (multiply by 12), add the remaining inches, then multiply the total by 2.54. For 5 feet 9 inches: (5 x 12) + 9 = 69 inches; 69 x 2.54 = 175.3 cm. The inches to cm converter handles this in one step.
What is the difference between millimetres and inches for precision work?
One inch is exactly 25.4 mm. At typical machining tolerances of plus or minus 0.1 mm, an inch-spec part may need conversion to three or four decimal places. For 3D printing, tolerances of 0.1 to 0.2 mm are typical; the mm to inch converter shows the result to five decimal places.
How do I read a metric ruler?
Each centimetre is divided into 10 millimetres, so the small marks between centimetre numbers represent 1 mm each. The halfway mark between two centimetre lines is 5 mm. A standard 30 cm ruler is about 11.8 inches. On an imperial ruler, the marks halve in size as the fraction doubles: half, quarter, eighth, sixteenth of an inch.