Unit conversion guide
Celsius to Fahrenheit Guide
How to convert Celsius to Fahrenheit, Fahrenheit to Celsius and Kelvin without mixing up the formula.
Updated 16 October 2026 • Reviewed by Tools by Layna Editorial Team • General information only
Celsius to Fahrenheit conversion is different from most unit conversions because it includes an offset. That is why a simple multiply or divide shortcut often gives the wrong result.
The formula
Celsius to Fahrenheit is °F = °C × 9 ÷ 5 + 32. Fahrenheit to Celsius is °C = (°F − 32) × 5 ÷ 9.
Examples
20°C is 68°F. 0°C is 32°F. 100°C is 212°F. Those three anchors make it easier to sanity-check a result.
Why the formula has +32
The two scales do not start at the same point. Fahrenheit places water freezing at 32°F, while Celsius places it at 0°C. That offset is why the extra step is needed.
Cooking and weather
Australian weather and most local appliance references use Celsius. US recipes and imported appliances may use Fahrenheit, so convert before changing oven settings.
Kelvin context
Kelvin is common in science. Kelvin equals Celsius plus 273.15. It is written as K, not degrees K.
Common mistake
People often multiply Celsius by 9/5 but forget to add 32, or subtract 32 after multiplying when converting Fahrenheit back to Celsius. Order matters.
Offsets, differences and reverse checks
Celsius and Fahrenheit do not share a common zero, so temperature conversion requires both scaling and an offset. Use °F = (°C × 9/5) + 32. The reverse formula is °C = (°F − 32) × 5/9. Multiplying by 1.8 without adding 32 converts a temperature difference, not an actual temperature reading.
A change of 1 °C equals a change of 1.8 °F, but 0 °C is 32 °F. This distinction matters when converting weather forecasts, oven temperatures and scientific ranges. For example, an increase from 20 °C to 25 °C is a 5 °C or 9 °F increase, while the endpoints are 68 °F and 77 °F.
Ovens can differ from their displayed setting, and fan-forced recipes may specify a lower temperature than conventional ovens. A mathematically correct conversion does not replace the recipe’s oven-mode instruction or calibration. Round to a setting the appliance can actually use and monitor cooking progress.
Use known reference points as a quick error check: water freezes at 0 °C or 32 °F and boils at about 100 °C or 212 °F at standard atmospheric pressure. A result that fails these checks usually used the formula in the wrong order.
Keep negative signs and brackets visible in the reverse formula. For example, converting 14 °F requires subtracting 32 before multiplying by 5/9; multiplying first gives the wrong result. A calculator avoids this order-of-operations mistake, but the displayed formula should still be checked when the value is below freezing.
Sources and review notes
- National Measurement Institute — Australia’s National Measurement Institute maintains Australia’s measurement system and primary measurement standards. Use official measurement standards where legal, trade or technical precision matters.