Celsius to Fahrenheit: Formula, Chart and Quick Tricks
By ToolNimba Editorial Team June 20, 2026 3 min read
Celsius and Fahrenheit are two scales for the same thing, temperature. Celsius is used by most of the world and sets water freezing at 0 degrees and boiling at 100. Fahrenheit, common in the United States, sets freezing at 32 degrees and boiling at 212. Converting between them is a two step calculation once you know the formula, and this guide walks through the exact maths, a quick mental trick, a full chart, and the questions people ask most.
Quick answer
To convert Celsius to Fahrenheit, multiply by 1.8 and add 32. For example, 20 C times 1.8 is 36, plus 32 gives 68 F. To go back, subtract 32 and divide by 1.8.
The Celsius to Fahrenheit formula
Formula
Fahrenheit = (Celsius times 9 divided by 5) + 32. In words: multiply by 1.8, then add 32.
The 9 divided by 5 part (which equals 1.8) stretches the Celsius scale to match the wider spacing of Fahrenheit degrees, and the plus 32 shifts the starting point so that the freezing point of water lines up correctly. Both steps matter, and skipping the plus 32 is the most common mistake people make.
Worked example, step by step
Suppose you want to convert 25 degrees Celsius, a warm spring afternoon, into Fahrenheit. Follow these steps in order.
- Start with the Celsius value: 25.
- Multiply by 1.8 (the same as 9 divided by 5): 25 times 1.8 equals 45.
- Add 32 to that result: 45 plus 32 equals 77.
- Read the answer: 25 degrees Celsius equals 77 degrees Fahrenheit.
The same three steps work for any value. For a temperature below freezing, the multiply step gives a negative number, but the method does not change. For example, minus 10 C times 1.8 is minus 18, plus 32 gives 14 F.
The reverse: Fahrenheit to Celsius
Formula
Celsius = (Fahrenheit minus 32) times 5 divided by 9. In words: subtract 32, then divide by 1.8.
To convert 98.6 F, body temperature: 98.6 minus 32 is 66.6, divided by 1.8 is 37. So 98.6 F equals 37 C. Notice the steps run in the opposite order from the forward formula, because you are undoing each operation: subtract before you divide, just as you multiplied before you added.
A quick mental shortcut
When you only need a rough answer, double the Celsius value and add 30. For 20 C that gives 70, close to the exact 68. The trick drifts a little at the extremes because it uses 2 instead of 1.8, but for everyday weather it is good enough to picture the temperature. If you want one fact to anchor everything, remember that minus 40 is the same number on both scales, the only point where Celsius and Fahrenheit meet.
Conversion chart
Common temperatures
| Celsius | Fahrenheit | Feels like |
|---|---|---|
| minus 40 | minus 40 | Both scales equal |
| minus 18 | 0 | Deep freezer |
| 0 | 32 | Freezing |
| 10 | 50 | Cool |
| 16 | 61 | Mild |
| 20 | 68 | Room temperature |
| 25 | 77 | Warm |
| 30 | 86 | Hot day |
| 37 | 98.6 | Body temperature |
| 40 | 104 | Heatwave |
| 100 | 212 | Water boils |
Oven temperatures for cooking
Recipes often switch between scales, so an oven chart saves you from second guessing. These are the rounded numbers most cookbooks use.
Common oven settings
| Celsius | Fahrenheit | Description |
|---|---|---|
| 140 | 275 | Very low |
| 160 | 325 | Low |
| 180 | 350 | Moderate |
| 200 | 400 | Hot |
| 220 | 425 | Very hot |
| 240 | 475 | Maximum for most ovens |
Where the two scales came from
Daniel Gabriel Fahrenheit proposed his scale in 1724, fixing reference points based on a brine mixture and the human body. Anders Celsius introduced his scale in 1742, anchored to the freezing and boiling points of water, which made it simpler for science. Most countries adopted Celsius as part of the metric system, while the United States kept Fahrenheit for everyday weather and cooking. Both describe the same physical reality, which is why a clean conversion always exists.
If you work in science you may also meet Kelvin, which starts at absolute zero. To reach Kelvin from Celsius you simply add 273.15, and our converter handles all three scales at once.
Convert any temperature instantly
The converter below switches between Celsius, Fahrenheit and Kelvin as you type, so you never have to reach for the formula.
🌡️ Try the free tool Temperature Converter Free temperature converter for Celsius, Fahrenheit and Kelvin. Convert C to F, F to C, C to K and back instantly, with exact formulas, fever and oven charts.Need other units? The same step by step approach powers our other guides, including how to calculate a percentage when a recipe scales up or down. The length and weight converters work the same way, with the method explained on each page.
Frequently asked questions
What is the formula to convert Celsius to Fahrenheit?
Multiply the Celsius value by 9 divided by 5 (that is 1.8), then add 32. For example, 25 C is 25 times 1.8 which is 45, plus 32 gives 77 F. The multiply step widens the scale and the add step shifts the zero point.
What is 37 degrees Celsius in Fahrenheit?
37 C is 98.6 F, the traditional figure for normal human body temperature. The maths is 37 times 1.8 equals 66.6, plus 32 equals 98.6. Many modern studies put the true average slightly lower, near 98.2 F.
Is there an easy way to estimate the conversion?
Yes. For a quick mental estimate, double the Celsius number and add 30. It runs slightly high because it uses 2 instead of 1.8, but it is close enough for everyday weather. For example, 20 C estimates to 70, while the exact answer is 68.
At what temperature are Celsius and Fahrenheit the same?
Minus 40 is the single point where both scales read the same number, so minus 40 C equals minus 40 F. It is the only crossover, and it makes a handy memory anchor when you are sanity checking a conversion at very cold temperatures.
What is 100 degrees Celsius in Fahrenheit?
100 C equals 212 F, the boiling point of water at sea level. Using the formula, 100 times 1.8 is 180, plus 32 gives 212. This pairing, along with freezing at 0 C and 32 F, defines the whole Celsius scale.
Why does the formula add 32?
The 32 accounts for the different zero points of the two scales. Water freezes at 0 C but at 32 F, so after stretching the scale by 1.8 you must shift it up by 32 degrees to line the freezing points up. Without it, every answer is off by 32.
How do I convert a fever reading like 38.5 C?
Multiply 38.5 by 1.8 to get 69.3, then add 32 for 101.3 F. That is a clear fever. Keeping the formula handy is useful when a thermometer reads in one scale but your reference for normal sits in the other.
Is Celsius or Fahrenheit more accurate?
Neither is more accurate, since both measure the same temperature. Fahrenheit has smaller degrees, so it offers slightly finer steps without decimals, while Celsius ties cleanly to water and the metric system. Accuracy depends on your thermometer, not the scale.