Convert Fahrenheit to Celsius

Converting Fahrenheit to Celsius does not mean memorizing a scary equation and doing arithmetic in your head. The exact conversion is a simple two-step subtraction and multiplication. The real challenge is knowing which number to trust. You need the right method and a few reference points. Here is the exact equation, a worked example, a quick-glance table, and a mental shortcut for everyday temperatures, along with the honest limits of that shortcut.

The formula to convert Fahrenheit to Celsius is °C = (°F - 32) × 5/9. Subtract 32 from the Fahrenheit temperature first, then multiply the result by five-ninths. The order matters: if you multiply before subtracting, you will get a wrong answer. For example, 68°F minus 32 equals 36, and 36 times 5/9 equals 20°C. That is the entire method. The 9/5 ratio is the exact conversion factor between the two scales, and the 32-degree offset accounts for the different zero points. This equation works for any temperature, from absolute zero to the surface of a star, so it is the only equation you need for an exact answer.

Take a common room temperature of 68°F. First, subtract 32 from 68, which gives you 36. Then multiply 36 by 5/9. Since 36 divided by 9 is 4, and 4 times 5 is 20, the answer is 20°C. That is a comfortable room temperature in most of the world. Now try a freezing point: 32°F minus 32 is 0, and 0 times 5/9 is 0°C, which is the freezing point of water. For a boiling point, 212°F minus 32 is 180, and 180 times 5/9 is 100°C, the boiling point of water at sea level. These three checks confirm the equation works. If you are converting a temperature like 98.6°F, which is the old average human body temperature, subtract 32 to get 66.6, then multiply by 5/9 to get 37°C. The modern average body temperature is actually closer to 97.5°F, or 36.4°C, so do not be alarmed if your thermometer reads lower.

For a fast reference, here is a compact chart of common temperatures in Fahrenheit and their Celsius equivalents. This covers weather, cooking, and body heat ranges. The full chart with every degree is linked below, but this gives you the everyday values you are most likely to need.

If you need a rough answer without pen and paper, use the double-and-subtract rule for Celsius to Fahrenheit, or its reverse for Fahrenheit to Celsius. To go from Fahrenheit to Celsius, subtract 30 from the Fahrenheit temperature, then divide by 2. For example, 68°F minus 30 is 38, and 38 divided by 2 is 19°C. The exact answer is 20°C, so the estimate is off by 1 degree. For a temperature like 50°F, subtract 30 to get 20, then divide by 2 to get 10°C, which matches the exact 10°C. This shortcut works well for typical outdoor weather between about 10°C and 25°C, which is roughly 50°F to 77°F. The error grows outside that range. At 0°F, the estimate gives -15°C instead of the exact -17.8°C, a difference of nearly 3 degrees. At 100°F, the estimate gives 35°C instead of the exact 37.8°C, a difference of nearly 3 degrees as well. So use the shortcut for a quick sense of the weather, but never for cooking, medicine, or science. For those, use the exact equation.

The Fahrenheit to Celsius converter takes a temperature value in Fahrenheit and returns the equivalent in Celsius. Enter the number in the input field, choose the conversion direction, and select how many decimal places you want. The converter also shows the calculation steps, so you can see exactly how the equation is applied, and it gives the Kelvin equivalent for scientific use. For example, if you enter 68°F, the converter returns 20°C and shows the steps: subtract 32, then multiply by 5/9. If you need to convert Celsius to Fahrenheit instead, switch the direction, and the tool uses the reverse equation. This is useful when you are reading a recipe from a country that uses Celsius, or when you are checking a weather forecast from a place that reports in Celsius. The converter is exact, so it does not suffer from the rounding errors of mental shortcuts.

Weather

Knowing how to convert Fahrenheit to Celsius matters most in three daily situations: weather, cooking, and health. If you travel to a country that uses Celsius, a weather forecast of 20°C means a light jacket, while 30°C means shorts.

Cooking

If you are baking a recipe from a US cookbook while living abroad, you need to convert 350°F to 180°C for a conventional oven. For fan-forced ovens, you typically reduce the temperature by about 20°C, so 180°C becomes 160°C.

Health

For body temperature, a reading of 100.4°F is the standard threshold for a fever in adults, which is 38°C. A reading of 99°F is 37.2°C, which is a high normal. These conversions are the difference between burning a cake, dressing wrong for the weather, or misjudging an illness.

One common misconception is that Celsius numbers are always lower than Fahrenheit numbers. That is only true above -40°, because -40°F equals -40°C, the point where the two scales meet. Below -40°, Fahrenheit numbers are lower. Another misconception is that the conversion equation is too complicated to learn. In reality, it is two arithmetic steps that you can practice until it becomes automatic. A third misconception is that Fahrenheit and Celsius measure different kinds of temperature. They do not; they are two different rulers for the same physical property. The difference is the zero point and the size of the degree. A Celsius degree is 9/5 larger than a Fahrenheit degree, which is why the conversion factor is 9/5. Understanding this makes the equation less mysterious and easier to remember.

The relationship between Fahrenheit and Celsius is linear, which means it is a straight line on a graph. The slope of that line is 9/5, meaning a change of 5 degrees Celsius equals a change of 9 degrees Fahrenheit. The intercept is 32, because 0°C corresponds to 32°F. This is why the equation has both a multiplication and a subtraction: the multiplication accounts for the different degree sizes, and the subtraction aligns the zero points. If you ever forget the equation, you can derive it from the freezing and boiling points of water. Water freezes at 0°C or 32°F and boils at 100°C or 212°F. The difference is 100 Celsius degrees and 180 Fahrenheit degrees, so the ratio is 180/100, which simplifies to 9/5. The offset is 32, because 0°C is 32°F. This derivation works every time.

When you travel internationally, the Fahrenheit to Celsius converter becomes your best friend. The United States, Liberia, and Myanmar are the only countries that use Fahrenheit as the primary scale for weather, so if you are from the US, you will need to convert forecasts, oven temperatures, and even fever readings. The United Kingdom uses Celsius officially, but many people still think in Fahrenheit for warm summer days, so you might hear both in casual conversation. Canada officially uses Celsius, but older generations often remember Fahrenheit, so you may need to convert in both directions. Australia and New Zealand have used Celsius exclusively since the 1970s, so a converter is less necessary there but still useful for US visitors. In every case, the converter gives you an exact answer, so you can plan your packing, set your oven, or decide whether to see a doctor without second-guessing the number.

The difference between Fahrenheit and Celsius comes down to the reference points and the size of the degree. Fahrenheit sets the freezing point of water at 32°F and the boiling point at 212°F, a difference of 180 degrees. Celsius sets the freezing point at 0°C and the boiling point at 100°C, a difference of 100 degrees. This makes Celsius more intuitive for scientific work, which is why most of the world uses it. Fahrenheit, on the other hand, has finer resolution for everyday temperatures, which is why it persists in the US for weather and cooking. The two scales meet at -40°, where both read -40. Below that, Fahrenheit numbers are lower; above that, Celsius numbers are lower. This is a useful check for your mental math: if you convert a temperature above -40 and the Celsius number is higher than the Fahrenheit number, you made a mistake.

The double-and-add-30 shortcut works in the opposite direction, but the failure case is important. To convert Celsius to Fahrenheit, double the Celsius number and add 30. For 20°C, doubling gives 40, and adding 30 gives 70°F, which is close to the exact 68°F. For 10°C, doubling gives 20, and adding 30 gives 50°F, which matches the exact 50°F. But for extreme temperatures, the shortcut fails badly. At 0°C, the shortcut gives 30°F instead of the exact 32°F, an error of 2 degrees. At 40°C, the shortcut gives 110°F instead of the exact 104°F, an error of 6 degrees. At -20°C, the shortcut gives -10°F instead of the exact -4°F, an error of 6 degrees. So use the shortcut only when you are in the range of typical outdoor weather, roughly 10°C to 25°C, and never for cooking or medical decisions. When the normal route of mental math fails, the converter is the reliable fallback.

For a complete list of every degree from -50°F to 250°F, the full chart is available in the converter output when you enter a value. The compact chart above covers the most common temperatures, but if you need a specific value like 72°F or 180°C, the converter gives you the exact answer instantly. The chart is particularly useful for oven temperatures: 325°F is 163°C, 350°F is 177°C, 375°F is 191°C, and 400°F is 204°C. For a fan-forced oven, subtract 20°C from these values. For example, 180°C becomes 160°C. These are the conversions that matter in the kitchen, and getting them wrong ruins recipes. The converter eliminates that risk.

What is the formula to convert Fahrenheit to Celsius?

Subtract 32 from the Fahrenheit value, then multiply by 5/9. The equation is °C = (°F - 32) × 5/9. For example, 68°F minus 32 is 36, and 36 times 5/9 is 20°C.

At what temperature are Fahrenheit and Celsius equal?

The two scales are equal at -40°. -40°F is exactly -40°C. This is the only temperature where both scales read the same number.

What is the freezing point of water in Fahrenheit and Celsius?

The freezing point of water is 32°F and 0°C. The boiling point is 212°F and 100°C. These are fixed by definition at standard pressure.

How do I convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5, then add 32. The equation is °F = (°C × 9/5) + 32. For example, 20°C times 9/5 is 36, and 36 plus 32 is 68°F.

Is there a quick way to estimate Fahrenheit to Celsius?

Subtract 30 and divide by 2. This works for typical outdoor weather between about 50°F and 77°F, but it is not accurate enough for cooking or medicine. Use the exact equation or the converter for those.

The mental shortcut of subtracting 30 and halving is good enough for a walk in the park, but it is a trap in the kitchen or the clinic. At 100°F, the shortcut gives 35°C instead of the exact 37.8°C, a difference that matters when you are measuring a fever or proofing yeast. At 0°F, the shortcut gives -15°C instead of -17.8°C, a difference that matters when you are dressing for a blizzard. The exact equation never fails, but it requires you to do multiplication with fractions, which is where most people make mistakes. The converter removes that risk, but if you are ever without a device, remember the three checkpoints: 0°C is 32°F, 20°C is 68°F, and 37°C is 98.6°F. These anchor points let you interpolate with reasonable accuracy. never trust the double-and-add-30 rule for any temperature below 50°F or above 77°F, because the error compounds faster than you think.