What is the formula for Fahrenheit to Celsius?

C = (F − 32) × 5/9. The 32 comes off first, because 32 °F and 0 °C are the same temperature and that offset has to go before any scaling; then the multiply by 5/9 handles the size of the degree, since a Celsius degree is 9/5 as large as a Fahrenheit one. The reverse is F = C × 9/5 + 32, which the swap button between the two boxes does for you: 37 °C comes back as 98.6 °F and 100 °C as 212 °F.

What is 70 °F in Celsius?

21.1111111111 °C. A few more of the temperatures people look up: 50 °F is 10 °C, 60 °F is 15.5555555556 °C, 75 °F is 23.8888888889 °C, 80 °F is 26.6666666667 °C and 90 °F is 32.2222222222 °C. For whole-number Fahrenheit inputs, Celsius is whole when F − 32 is a multiple of 9, which is why 41 °F is exactly 5 °C and 68 °F exactly 20 °C while the values in between run to repeating decimals.

How do I convert F to C in my head?

Subtracting 30 and halving gives an approximation. At 50 °F it gives exactly 10 °C, at 70 °F it gives 20 °C against the displayed 21.1111111111 °C, and at 32 °F it gives 1 °C instead of 0 °C. The shortcut is high below 50 °F and low above it; at 212 °F it gives 91 °C instead of 100 °C. Use (F − 32) × 5/9 for the defined scale conversion.

Why is 98.6 °F exactly 37 °C?

The defined scale equation gives 37 × 9/5 + 32 = 98.6 exactly. No rounding is needed for that mathematical pair: entering 98.6 °F gives 37 °C, and reversing the units converts 37 °C to 98.6 °F. This is conversion of a stated temperature, not an assessment of a person’s body temperature.

Where do Fahrenheit and Celsius meet?

At −40. Set the two scales equal in C = (F − 32) × 5/9 and −40 is the only solution, so −40 °F is −40 °C and nothing needs converting. It is also a quick test of whether a converter has its offset the right way round: a page that only multiplies will tell you 0 °F is 0 °C, and 0 °F is −17.7777777778 °C.

Is the decimal exact, or is it rounded?

The definition is exact; the decimal usually is not. Five ninths is a repeating fraction, so most Fahrenheit readings land on a repeating decimal: 0 °F is −17.777777... and the page shows −17.7777777778, twelve significant digits with the last one rounded. For whole-number Fahrenheit inputs, multiples of 9 in F − 32 give whole Celsius results: 32 °F is 0 °C, 41 °F is 5 °C, 68 °F is 20 °C, 104 °F is 40 °C and 212 °F is 100 °C. The converter uses rational arithmetic for the written decimal and exact scale equation. These are absolute temperatures; a temperature difference uses only the scale factor. Below-absolute-zero inputs are labeled as arithmetic that names no real temperature.

What is 350 °F in Celsius for an oven?

The scale conversion displays 350 °F as 176.666666667 °C, 400 °F as 204.444444444 °C and 425 °F as 218.333333333 °C. Those rounded decimal outputs do not choose an oven setting, account for calibration or change a recipe’s fan/conventional-oven instructions. Copy result copies the displayed number; Copy complete conversion includes input, units and conventions and remains selectable if native copying is refused.

Can I see Kelvin and Rankine as well?

Kelvin is already there. Under the answer the page lists the same temperature in every common unit of the category, so 98.6 °F shows as 37 °C and 310.15 K together, and each row has its own copy button. Rankine is marked as an uncommon unit, so it appears when you switch on Uncommon units in the readout strip, which adds the one extra row: 98.6 °F is 558.27 °R.

Will the page still open on Fahrenheit and Celsius if I last converted something else?

This focused page opens on Fahrenheit and Celsius, while preserving the main converter’s saved unit pair. When storage is usable, a saved value and uncommon-unit preference can travel between pages. Its suffix must still match the current From unit. Valid deliberate scalar edits can save those fields after a short delay; invalid or incomplete drafts do not overwrite the saved record. Unusable or conflicting records are kept with an explanation until you use Forget saved settings, which keeps the current conversion on screen.

F to C Calculator

Fahrenheit to Celsius is the one everyday conversion where you cannot just multiply: the two scales start in different places, so the offset comes off before the scaling. C = (F − 32) × 5/9. That gives the anchor values people check a converter against: 32 °F is 0 °C, 212 °F is 100 °C, 98.6 °F is 37 °C, and −40 °F is −40 °C, the single temperature where the two scales read the same number. This page opens the converter already set to Fahrenheit and Celsius, ahead of whatever pair you last used, converts as you type to twelve significant digits, and lists the same temperature in Kelvin underneath, with Rankine behind the Uncommon units switch.

From

To-17.2222222222

Category: Temperature

Base unit: kelvin

Uncommon units: Show 1 more

These are absolute temperatures with scale offsets, not temperature differences. Values below absolute zero are labeled as arithmetic only.

Results round to 12 significant digits using the listed unit definitions. Input must have a finite numeric magnitude and at most 512 significant digits. Type a single decimal or scientific number; a matching From unit suffix is accepted. Commas and grouped spaces separate thousands; decimal commas, fractions and compound measurements are refused.

1 °F in every temperature unit

Celsius°C
-17.2222222222
KelvinK
255.927777778

Selectable complete conversion

Unit Converter — Temperature
Input: 1 (Fahrenheit, °F)
Result: -17.2222222222 °C (Celsius)
Displayed values round to 12 significant digits.
These are absolute temperatures with scale offsets, not temperature differences. Values below absolute zero are labeled as arithmetic only.
All other units:
Celsius (°C): -17.2222222222
Kelvin (K): 255.927777778
Rankine (°R): 460.67

Common questions

What is the formula for Fahrenheit to Celsius?: C = (F − 32) × 5/9. The 32 comes off first, because 32 °F and 0 °C are the same temperature and that offset has to go before any scaling; then the multiply by 5/9 handles the size of the degree, since a Celsius degree is 9/5 as large as a Fahrenheit one. The reverse is F = C × 9/5 + 32, which the swap button between the two boxes does for you: 37 °C comes back as 98.6 °F and 100 °C as 212 °F.
What is 70 °F in Celsius?: 21.1111111111 °C. A few more of the temperatures people look up: 50 °F is 10 °C, 60 °F is 15.5555555556 °C, 75 °F is 23.8888888889 °C, 80 °F is 26.6666666667 °C and 90 °F is 32.2222222222 °C. For whole-number Fahrenheit inputs, Celsius is whole when F − 32 is a multiple of 9, which is why 41 °F is exactly 5 °C and 68 °F exactly 20 °C while the values in between run to repeating decimals.
How do I convert F to C in my head?: Subtracting 30 and halving gives an approximation. At 50 °F it gives exactly 10 °C, at 70 °F it gives 20 °C against the displayed 21.1111111111 °C, and at 32 °F it gives 1 °C instead of 0 °C. The shortcut is high below 50 °F and low above it; at 212 °F it gives 91 °C instead of 100 °C. Use (F − 32) × 5/9 for the defined scale conversion.
Why is 98.6 °F exactly 37 °C?: The defined scale equation gives 37 × 9/5 + 32 = 98.6 exactly. No rounding is needed for that mathematical pair: entering 98.6 °F gives 37 °C, and reversing the units converts 37 °C to 98.6 °F. This is conversion of a stated temperature, not an assessment of a person’s body temperature.
Where do Fahrenheit and Celsius meet?: At −40. Set the two scales equal in C = (F − 32) × 5/9 and −40 is the only solution, so −40 °F is −40 °C and nothing needs converting. It is also a quick test of whether a converter has its offset the right way round: a page that only multiplies will tell you 0 °F is 0 °C, and 0 °F is −17.7777777778 °C.
Is the decimal exact, or is it rounded?: The definition is exact; the decimal usually is not. Five ninths is a repeating fraction, so most Fahrenheit readings land on a repeating decimal: 0 °F is −17.777777... and the page shows −17.7777777778, twelve significant digits with the last one rounded. For whole-number Fahrenheit inputs, multiples of 9 in F − 32 give whole Celsius results: 32 °F is 0 °C, 41 °F is 5 °C, 68 °F is 20 °C, 104 °F is 40 °C and 212 °F is 100 °C. The converter uses rational arithmetic for the written decimal and exact scale equation. These are absolute temperatures; a temperature difference uses only the scale factor. Below-absolute-zero inputs are labeled as arithmetic that names no real temperature.
What is 350 °F in Celsius for an oven?: The scale conversion displays 350 °F as 176.666666667 °C, 400 °F as 204.444444444 °C and 425 °F as 218.333333333 °C. Those rounded decimal outputs do not choose an oven setting, account for calibration or change a recipe’s fan/conventional-oven instructions. Copy result copies the displayed number; Copy complete conversion includes input, units and conventions and remains selectable if native copying is refused.
Can I see Kelvin and Rankine as well?: Kelvin is already there. Under the answer the page lists the same temperature in every common unit of the category, so 98.6 °F shows as 37 °C and 310.15 K together, and each row has its own copy button. Rankine is marked as an uncommon unit, so it appears when you switch on Uncommon units in the readout strip, which adds the one extra row: 98.6 °F is 558.27 °R.
Will the page still open on Fahrenheit and Celsius if I last converted something else?: This focused page opens on Fahrenheit and Celsius, while preserving the main converter’s saved unit pair. When storage is usable, a saved value and uncommon-unit preference can travel between pages. Its suffix must still match the current From unit. Valid deliberate scalar edits can save those fields after a short delay; invalid or incomplete drafts do not overwrite the saved record. Unusable or conflicting records are kept with an explanation until you use Forget saved settings, which keeps the current conversion on screen.

Results round to 12 significant digits using the listed unit conventions. Many factors are exact definitions; psi and parsec use rounded coefficients. Temperature includes scale offsets. Days and weeks are fixed-duration units, and unit conversion does not determine calendar dates, ambient pressure or a software label’s convention.