Celsius to Fahrenheit Converter

What is the Celsius to Fahrenheit conversion?

Celsius to Fahrenheit conversion turns a temperature on the Celsius (°C) scale into its equivalent on the Fahrenheit (°F) scale using the formula °F = (°C × 9/5) + 32. The two scales measure the same physical temperature; they simply use different starting points and different degree sizes, so a single number has two different labels.

This converter goes further and shows Celsius, Fahrenheit and Kelvin together. Type any value, pick its scale, and all three update at once — handy when a recipe, weather forecast or science problem mixes systems.

How do you convert Celsius to Fahrenheit?

Multiply the Celsius figure by 9/5 (which equals 1.8), then add 32. The “×9/5” accounts for Fahrenheit degrees being smaller, and the “+32” shifts the zero point, because water freezes at 0°C but 32°F.

The exact formulas this tool uses are:

• Celsius → Fahrenheit: °F = (°C × 9/5) + 32
• Fahrenheit → Celsius: °C = (°F − 32) × 5/9
• Celsius → Kelvin: K = °C + 273.15
• Kelvin → Celsius: °C = K − 273.15

Results are rounded to two decimal places.

Worked example 1 — 20°C to Fahrenheit

Take a pleasant 20°C spring day:

1. Multiply: 20 × 9/5 = 20 × 1.8 = 36
2. Add 32: 36 + 32 = 68

So 20°C = 68°F, and in Kelvin 20 + 273.15 = 293.15 K.

Worked example 2 — 98.6°F to Celsius

Now reverse it for normal body temperature:

1. Subtract 32: 98.6 − 32 = 66.6
2. Multiply by 5/9: 66.6 × 5/9 = 37

So 98.6°F = 37°C — exactly the body-temperature figure people remember. (Convert it onward and 37 + 273.15 = 310.15 K.)

Why are there 9/5 and 32 in the formula?

Because the two scales were built around different reference points. Fahrenheit puts the freezing point of water at 32° and boiling at 212°, a 180-degree span. Celsius puts freezing at 0° and boiling at 100°, a 100-degree span. Dividing 180 by 100 gives the 9/5 ratio between degree sizes, and the 32 corrects for the offset freezing point.

A useful consequence: there is exactly one temperature where the scales meet. Solving °C = (°C × 9/5) + 32 gives −40, which is why −40°C = −40°F.

Celsius to Fahrenheit to Kelvin reference chart

Use this table to check the converter or for quick mental conversions. Values are rounded to two decimals.

Celsius (°C)	Fahrenheit (°F)	Kelvin (K)	What it is
−40	−40	233.15	Where the scales cross
−17.78	0	255.37	0°F
−10	14	263.15	Hard freeze
0	32	273.15	Water freezes
10	50	283.15	Cool day
20	68	293.15	Room temperature
25	77	298.15	Warm day
30	86	303.15	Hot day
37	98.6	310.15	Body temperature
40	104	313.15	High fever / heatwave
50	122	323.15	Extreme heat
100	212	373.15	Water boils

Key points to remember

• Freezing: 0°C = 32°F
• Room temperature: ~20°C = 68°F
• Body temperature: 37°C = 98.6°F
• Boiling: 100°C = 212°F
• Absolute zero: 0 K = −273.15°C = −459.67°F

What about oven and cooking temperatures?

Recipes written in different countries assume different scales, so converting is essential for baking. Note that ovens are usually set in round numbers, so the exact Fahrenheit value is rounded to the nearest convenient mark.

Celsius (°C)	Exact °F	Recipe °F	Gas mark	Description
140	284	275	1	Very slow
160	320	325	3	Slow / warm
180	356	350	4	Moderate (most baking)
200	392	400	6	Moderately hot
220	428	425	7	Hot

So when a UK recipe says 180°C, set a US oven to 350°F.

Where did the Celsius and Fahrenheit scales come from?

Daniel Gabriel Fahrenheit, a German-Dutch physicist, introduced his scale in 1724, originally anchoring 0° to a freezing brine mixture and ~96° to body temperature; it was later standardised to freezing (32°) and boiling (212°) water. Anders Celsius, a Swedish astronomer, proposed his 100-degree scale in 1742 (curiously, with 0 as boiling and 100 as freezing — soon reversed to today’s form).

Kelvin, devised by William Thomson (Lord Kelvin) in 1848, is the SI base unit. It uses Celsius-sized degrees but starts at absolute zero, the coldest temperature physically possible, where molecular motion is minimal. That is why scientists prefer Kelvin: it never goes negative.

Real-world use cases

• Travel and weather: translating a forecast from a country that uses the other scale.
• Cooking and baking: converting oven temperatures between metric and US recipes (see the chart above).
• Health: reading a thermometer and judging a fever. The figures here are general information, not medical advice — if you are worried about a temperature reading, consult a healthcare professional. For another quick health check, see our BMI calculator.
• Science and homework: converting lab data to Kelvin for gas-law calculations.
• Manufacturing and HVAC: matching equipment specs across regions.

Tips and common mistakes

• Don’t forget the +32. Multiplying by 1.8 alone gives the wrong answer for anything except 0°C. 25 × 1.8 = 45, but 25°C is actually 77°F.
• Order of operations on the reverse formula. Subtract 32 before multiplying by 5/9, not after.
• Kelvin uses 273.15, not 273. The 0.15 matters for precise work, though many quick references round it off.
• A 1°C change is a 1.8°F change. Differences scale by 1.8; the +32 offset applies only to absolute readings, not to gaps between them.
• Negative numbers still work. −10°C correctly gives 14°F because the formula handles the sign automatically.

Accuracy and limitations

The formula is exact — temperature conversion is pure arithmetic with no estimation involved. The only rounding here is to two decimal places in the displayed result, which is far finer than any household thermometer or oven dial can resolve. For laboratory or engineering work that needs more decimals, carry the full unrounded value through your own calculation.

For more measurement tools, browse the converters category.