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Unit Converter
Convert between length, weight, temperature, volume, area and speed units both directions — with the exact SI/NIST conversion factor, a table of nearby values, and a live re-converter. Temperature uses the affine °C/°F/K formula (not a naive multiply), and US and UK volume units (gallon, pint, fluid ounce) are handled distinctly. Computed entirely in your browser. Accurate, instant and free — for United States.
50 cm = 19.685 in.
50 cm in inch
19.685 in
1 cm = 0.3937 in — multiply by the exact factor.
1 cm =
0.3937 in
1 in =
2.54 cm
Nearby values
| Centimetre (cm) | Inch (in) |
|---|---|
| 45 | 17.717 |
| 46 | 18.11 |
| 47 | 18.504 |
| 48 | 18.898 |
| 49 | 19.291 |
| 50 | 19.685 |
| 51 | 20.079 |
| 52 | 20.472 |
| 53 | 20.866 |
| 54 | 21.26 |
| 55 | 21.654 |
How we calculate
How we calculate this
Reviewed by Reckonist Editorial · Last reviewed July 2026. Figures follow the methods and sources set out in our editorial standards.
Conversions use exact SI/NIST definitional factors (e.g. 1 in = 2.54 cm, 1 lb = 0.45359237 kg); temperature uses the affine °C/°F/K formulas. Displayed figures are rounded for readability — the underlying calculation is full-precision.
NIST · SI definitions
Take it further: find the span between any two dates with the Date Difference Calculator.
How the converter works — a single base factor
For every dimension — length, mass, volume, area and speed — each unit is stored as a factor to one base unit (metre, kilogram, litre, square metre, metre per second). To convert, the value is scaled to the base and back out to the target unit. That keeps every pair consistent and reversible, and it means the exact same engine converts both directions.
Scale to base
value × from-factor
result = value × from.factor ÷ to.factor
Each factor is how many base units are in one of that unit — exact by definition.
Both directions
reverse = swap factors
1 to = to.factor ÷ from.factor · from
The Swap button flips the pair; the answer updates instantly.
- 1Factor: 1 inch is exactly 2.54 cm.
- 2Convert: 50 ÷ 2.54 = 19.685 inches.
- 3Nearby: the table reads off 48–52 cm without retyping — e.g. 51 cm = 20.079 in.
Temperature is affine — not a simple multiply
Temperature is the one dimension that cannotbe a single factor, because Celsius and Fahrenheit don’t share a zero point. It needs both a scale and an offset: °F = °C × 9/5 + 32 and K = °C + 273.15. That is why 20 °C is 68 °F, not 36 °F. The converter special-cases temperature and applies the affine formula, so it is always right.
The classic bug
Exact SI / NIST factors, not rounded guesses
Every linear factor is the exact definitional value: 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 mile = 1609.344 m, 1 US gallon = 3.785411784 L. Only the answer shown on screen is rounded for readability — the calculation itself uses the full-precision constant, so repeated or chained conversions don’t drift.
Runs entirely in your browser
US and UK volume units are different sizes
A US gallon is 3.785411784 L; a UK (imperial) gallonis 4.54609 L — about 20% larger. The same gap applies to pints and fluid ounces. This converter labels US and UK volume units distinctly so recipe quantities and fuel-economy figures don’t silently mix systems.
Which one do I want?
The nearby-values table
Below the answer is a small table that converts a few values above and below your number, so you can compare a whole neighbourhood — say 48–52 cm in inches — without changing the input each time. It is built for sizing charts, shopping and quick lookups where a small range is more useful than one point answer.
Frequently asked questions
Divide the centimetres by 2.54, because 1 inch is exactly 2.54 cm by definition. For example, 50 cm ÷ 2.54 = 19.685 inches. The converter does this for you and also shows the exact factor (1 cm = 0.3937 in) plus a table of nearby values so you can read off 48, 49, 51 and 52 cm without retyping.
For linear units, yes — every factor is the exact definitional value, not a rounded approximation. 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 mile = 1609.344 m, 1 US gallon = 3.785411784 L. Only the displayed answer is rounded for readability; the underlying calculation uses the full-precision factor. Temperature uses the exact affine formula rather than a factor.
Because the Celsius and Fahrenheit scales do not share a zero point, so there is no single number you can multiply by. Converting temperature is affine — it needs both a scale and an offset: °F = °C × 9/5 + 32, and K = °C + 273.15. That is why 20 °C is 68 °F, not 36 °F. The converter special-cases temperature and applies the offset formula, so it is always correct.
They are different sizes. A US gallon is 3.785411784 litres; a UK (imperial) gallon is 4.54609 litres — about 20% larger. The same mismatch applies to pints and fluid ounces. This converter labels US and UK volume units distinctly (US gallon vs UK gallon) so you never mix them up, which is a common source of recipe and fuel-economy errors.
It converts the whole neighbourhood of your number in one glance — a few values above and below what you entered — so you can compare, say, 48–52 cm in inches without changing the input each time. It is handy for sizing charts, shopping and quick lookups where you want a small range rather than a single point answer.
Yes. Every conversion is computed locally in your browser from the built-in factors — nothing you type is sent to a server, there is no sign-up, and nothing is stored. That also means it works offline once the page has loaded.
Method & references
Methodology: linear units convert through a base unit (length = m, mass = kg, volume = L, area = m², speed = m/s) using exact definitional factors — 1 in = 2.54 cm, 1 lb = 0.45359237 kg, 1 mi = 1609.344 m, 1 US gal = 3.785411784 L, 1 UK gal = 4.54609 L. Temperature is affine (°F = °C × 9/5 + 32; K = °C + 273.15), not a multiply. Displayed answers are rounded; the underlying maths keeps full precision. All conversions run client-side and nothing is stored.
Cross-links
How we calculate this
Reviewed by Reckonist Editorial · Last reviewed July 2026. Figures follow the methods and sources set out in our editorial standards.
Conversions use exact SI/NIST definitional factors; temperature uses the affine °C/°F/K formulas. US and UK volume units are handled distinctly. Displayed results are rounded for readability.
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