Celsius to Fahrenheit: Formula, Quick Trick and Chart
By Ali Hamza · Published · 5 min read
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To convert Celsius to Fahrenheit, multiply by 9/5 (1.8) and add 32: °F = °C × 1.8 + 32. So 20 °C is 20 × 1.8 + 32 = 68 °F. To go the other way, subtract 32 and multiply by 5/9: °C = (°F − 32) ÷ 1.8, so 100 °F is about 37.8 °C. For a quick estimate in your head, double the Celsius and add 30; it is close enough for weather. ToolMany's Unit Converter does the exact calculation instantly, including Kelvin.
The formulas
| From → to | Formula | Example |
|---|---|---|
| Celsius → Fahrenheit | °F = °C × 9/5 + 32 | 25 °C → 77 °F |
| Fahrenheit → Celsius | °C = (°F − 32) × 5/9 | 50 °F → 10 °C |
| Celsius → Kelvin | K = °C + 273.15 | 25 °C → 298.15 K |
| Kelvin → Celsius | °C = K − 273.15 | 300 K → 26.85 °C |
Why 9/5 and 32? Water freezes at 0 °C and 32 °F, and boils (at sea level) at 100 °C and 212 °F. So 100 Celsius degrees span the same range as 180 Fahrenheit degrees: a ratio of 180/100 = 9/5. The +32 shifts the zero point.
The mental shortcut
Celsius → Fahrenheit: double it and add 30.
- 10 °C → 20 + 30 = 50 °F (exact: 50 °F)
- 20 °C → 40 + 30 = 70 °F (exact: 68 °F)
- 30 °C → 60 + 30 = 90 °F (exact: 86 °F)
Fahrenheit → Celsius: subtract 30 and halve it.
- 80 °F → 50 ÷ 2 = 25 °C (exact: 26.7 °C)
The shortcut is good for weather between about 0 and 30 °C, and drifts further off at higher temperatures. Do not use it for cooking or medical readings; use the exact formula or the converter.
A neat fact for checking: −40 is the same in both scales. −40 °C = −40 °F.
Common temperatures chart
Weather
| °C | °F | Feels like |
|---|---|---|
| −10 | 14 | Very cold |
| 0 | 32 | Freezing point of water |
| 10 | 50 | Cool |
| 15 | 59 | Mild |
| 20 | 68 | Pleasant room temperature |
| 25 | 77 | Warm |
| 30 | 86 | Hot |
| 35 | 95 | Very hot |
| 40 | 104 | Extreme heat |
Body temperature
| °C | °F |
|---|---|
| 36.5–37.0 | 97.7–98.6 (typical normal range) |
| 37.5 | 99.5 |
| 38.0 | 100.4 (commonly used as a fever threshold) |
| 39.0 | 102.2 |
| 40.0 | 104.0 |
Normal body temperature varies by person, time of day and where it is measured. Thresholds for fever differ between health services. This table is for unit conversion only, not medical advice; follow your doctor's or local health service's guidance.
Oven temperatures
| °C | °F | Typical use |
|---|---|---|
| 150 | 302 (often written 300) | Slow baking |
| 160 | 320 (often 325) | Cakes |
| 180 | 356 (often 350) | Most baking |
| 200 | 392 (often 400) | Roasting |
| 220 | 428 (often 425) | High-heat roasting |
| 230 | 446 (often 450) | Pizza, bread |
Recipes round oven temperatures to convenient numbers, so 180 °C and 350 °F are treated as equivalent even though 350 °F is 176.7 °C. Ovens vary by more than that anyway.
Fan (convection) ovens: many recipes suggest reducing the temperature by about 20 °C (roughly 25 °F) for fan ovens. Check the recipe and your oven's manual.
Cooking and food safety
| °C | °F | Meaning |
|---|---|---|
| 0 | 32 | Water freezes |
| 4 | 39 | Typical fridge setting |
| −18 | 0 | Typical freezer setting |
| 63 | 145 | Example safe minimum for some cooked meats |
| 74 | 165 | Example safe minimum for poultry and reheated food |
| 100 | 212 | Water boils at sea level |
Food-safety temperatures vary by country and type of food; follow your local food-safety authority's guidance.
Which countries use Fahrenheit?
The United States uses Fahrenheit for everyday temperatures, and a few other places do too. Most of the world uses Celsius for weather, cooking and medicine. Science uses Celsius and Kelvin. If you read a US recipe, weather report or thermostat, you will see Fahrenheit.
Kelvin in one paragraph
Kelvin is the scientific temperature scale. It starts at absolute zero, the coldest possible temperature (−273.15 °C), and its steps are the same size as Celsius degrees. There are no negative Kelvin temperatures, and it is written without a degree sign: 300 K, not 300 °K. You will mostly meet it in science, and in colour temperature for light bulbs and photography (a "2700 K" bulb gives warm light; "6500 K" is cool daylight).
Converting temperature differences
A temperature change converts differently from a temperature reading. A rise of 10 °C is a rise of 18 °F (multiply by 1.8, but do not add 32). This matters when someone says "it will be 5 degrees warmer tomorrow" or "lower the oven by 20 degrees".
Converting in a spreadsheet
If you have a column of readings to convert, a spreadsheet formula is quicker than doing them one by one. With a Celsius value in cell A2:
- Fahrenheit:
=A2*9/5+32 - Kelvin:
=A2+273.15
And with Fahrenheit in A2, Celsius is =(A2-32)*5/9. Fill the formula down the column, and round the results to one decimal place for everyday use. Excel and Google Sheets also have a built-in CONVERT function, for example =CONVERT(A2,"C","F").
Thermostats and home heating
Home thermostats in Celsius usually move in steps of 0.5 °C, and Fahrenheit thermostats in steps of 1 °F, which is a smaller step (about 0.56 °C). A common comfortable indoor setting is about 19–21 °C, or roughly 66–70 °F, though comfort varies from person to person and with humidity.
Using the converter
Open the Unit Converter, choose Temperature, pick the units and type a value. The result updates as you type, and you can convert between °C, °F and K in any direction. The same tool converts length, weight, volume, area, speed and digital storage, useful when a foreign recipe also lists ingredients in cups or ounces (see our guide to cooking conversions).
Frequently asked questions
What is the formula for Celsius to Fahrenheit?
°F = °C × 9/5 + 32. For example, 30 °C × 1.8 + 32 = 86 °F.
What is 37 °C in Fahrenheit?
98.6 °F, the traditional figure for normal body temperature.
What is 350 °F in Celsius?
About 177 °C. Recipes usually treat it as 180 °C.
At what temperature are Celsius and Fahrenheit equal?
At −40 degrees.
Is the quick trick accurate?
Within a few degrees for everyday weather. Use the exact formula for cooking and medical readings.
