What is the formula to convert Fahrenheit to Celsius?

Subtract 32 from the Fahrenheit value, then multiply by 5/9. Written as a formula: °C = (°F − 32) × 5/9. For example, 98.6 °F becomes (98.6 − 32) × 5/9 = 66.6 × 0.5556 = 37 °C.

What is the formula to convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5 (which is 1.8), then add 32. Written as a formula: °F = °C × 9/5 + 32. For example, 100 °C becomes 100 × 1.8 + 32 = 212 °F.

What is 98.6 °F in Celsius?

98.6 °F is exactly 37 °C, which is the standard normal adult body temperature. The Fahrenheit figure 98.6 was derived by Daniel Gabriel Fahrenheit and later standardised as a convenient round number on the Celsius scale.

What is 72 °F in Celsius?

72 °F is approximately 22.2 °C, a comfortable room temperature commonly used as a thermostat target in homes and offices. The exact calculation is (72 − 32) × 5/9 = 40 × 0.5556 = 22.222 °C.

At what temperature are Fahrenheit and Celsius the same?

The two scales cross at −40 degrees, meaning −40 °F equals −40 °C exactly. You can verify this with either formula.

Why does the US use Fahrenheit while most of the world uses Celsius?

Fahrenheit was introduced in the early 1700s and became established in English-speaking countries before the metric system was standardised. The US retained it after most other nations switched to Celsius (part of the SI metric system) during the 19th and 20th centuries. The UK officially uses Celsius but Fahrenheit remains widely understood for weather.

Fahrenheit to Celsius Converter

The Fahrenheit to Celsius converter lets you type a temperature in either scale and see the other value update instantly, with the full step-by-step arithmetic shown on demand. Whether you are checking a weather forecast, following an American recipe, reading a medical chart, or programming a thermostat, this tool gives you the exact answer in under a second — no rounding, no tables to scan, no guesswork.

The formula

There are two exact conversion formulas, derived from the definition of both scales:

Converting °F → °C (subtract the ice-point offset, then scale):

°C = (°F − 32) × 5/9

Converting °C → °F (scale up, then add the ice-point offset):

°F = °C × 9/5 + 32

The factor 5/9 (≈ 0.5556) exists because a Fahrenheit degree is exactly 5/9 the size of a Celsius degree. Fahrenheit placed water’s freezing point at 32 °F and boiling at 212 °F, giving a span of 180 °F across what Celsius covers in 100 °C — hence the 9/5 ratio between them.

Worked example

Problem: a recipe calls for a 350 °F oven. What is that in Celsius?

Start: 350 °F
Subtract 32: 350 − 32 = 318
Multiply by 5/9: 318 × 5/9 = 1590/9 = 176.67 °C

So set your oven to approximately 177 °C (or Gas Mark 4 in UK gas ovens).

Reverse example: 20 °C room temperature in Fahrenheit:

Start: 20 °C
Multiply by 9/5: 20 × 1.8 = 36
Add 32: 36 + 32 = 68 °F

Key reference temperatures

Point	°F	°C
Absolute zero	−459.67	−273.15
Water freezes	32	0
Room temperature	68–72	20–22
Normal body temperature	98.6	37
Water boils (sea level)	212	100
Moderate oven	350	176.67

The two scales are equal at −40°, the only temperature where both readings are identical — a useful sanity-check if you ever need to verify a formula mentally.

Why the formulas look the way they do

The offset of 32 comes from Fahrenheit’s choice of 32 as his ice-point. The 9/5 factor comes from his choice of 180 degrees between freezing and boiling (compared to Celsius’s 100 degrees). 180/100 simplifies to 9/5. Both formulas are algebraic inverses: applying one and then the other always returns you to the original value.

Celsius (formerly called centigrade) is anchored to water: 0 °C = freezing, 100 °C = boiling at sea-level standard pressure. This makes it far more intuitive for everyday science and cooking. Fahrenheit’s original anchors were a brine solution and human body temperature — neither of which are as reproducible — so Celsius was adopted as the global scientific standard.