What is the formula for Fahrenheit to Celsius?

The formula is: Celsius = (Fahrenheit - 32) x 5/9. For example, 100F = (100 - 32) x 5/9 = 37.78C. The formula accounts for the different zero points and scale sizes of the two systems.

What temperature is the same in both Fahrenheit and Celsius?

The two scales meet at minus 40 degrees. At -40F = -40C, the readings are identical. This is a useful mathematical curiosity but not one you are likely to experience in the UK, where temperatures rarely fall below -15C (5F).

How do I quickly estimate Fahrenheit from Celsius?

A handy trick is to double the Celsius value and add 30. This gives a rough estimate that is accurate enough for everyday use. For example, 20C: double = 40, plus 30 = 70F (actual: 68F). For precision, use the full formula or this converter.

Fahrenheit to Celsius Converter

Convert Fahrenheit to Celsius and Celsius to Fahrenheit

Published by UltraCalculatorsLast reviewed: 1 Apr 2026v1.0Report an issue

Fahrenheit remains the standard temperature scale in the United States, while the United Kingdom and most of the world use Celsius. This creates frequent confusion when reading American weather forecasts, following US-based recipes, or trying to understand temperature references in American media. When a heatwave in California hits 104F, what does that actually feel like in terms we understand? The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit in 1724, setting 32F as the freezing point of water and 212F as its boiling point. Celsius (originally called centigrade) uses a cleaner 0 to 100 scale for the same range. The conversion formula, C = (F - 32) x 5/9, reflects both the offset between the two zero points and the different size of each degree. This converter translates between the two scales instantly, and also shows the Kelvin equivalent for scientific contexts. Whether you are adjusting an American recipe for your UK oven, interpreting a weather forecast from a US city, or checking scientific data, this tool provides an immediate, precise answer.

How to Use This Calculator

To use the Fahrenheit to Celsius converter: 1. Select the conversion direction. Choose "Fahrenheit to Celsius" if you have a temperature in F and need the Celsius equivalent. Choose "Celsius to Fahrenheit" for the reverse. 2. For F to C: Enter the Fahrenheit temperature. The converter shows the Celsius result, the Kelvin equivalent, and a description of how that temperature generally feels. 3. For C to F: Enter the Celsius temperature. The converter shows the Fahrenheit result with the same additional context. 4. Results update instantly, so you can quickly check a range of temperatures without waiting.

How It Works

The conversion formulas are: Fahrenheit to Celsius: C = (F - 32) x 5/9 Example: 98.6F (body temperature) = (98.6 - 32) x 5/9 = 66.6 x 0.5556 = 37.0C Celsius to Fahrenheit: F = C x 9/5 + 32 Example: 20C (comfortable room) = 20 x 1.8 + 32 = 36 + 32 = 68F Kelvin (for both): K = C + 273.15 The scales cross at exactly -40 degrees, where -40F equals -40C. Each Fahrenheit degree is 5/9 the size of a Celsius degree, which is why Fahrenheit numbers tend to be larger.

Worked Examples

Example 1: Converting a US recipe oven temperature

Inputs: Fahrenheit: 350. Direction: F to C.

Celsius = (350 - 32) x 5/9.
= 318 x 0.5556.
= 176.67C.
Kelvin = 176.67 + 273.15 = 449.82 K.

Result: 350F equals approximately 177C, which is Gas Mark 4 in UK ovens.

Example 2: Understanding a US heatwave temperature

Inputs: Fahrenheit: 104. Direction: F to C.

Celsius = (104 - 32) x 5/9.
= 72 x 0.5556.
= 40.0C.

Result: 104F equals 40C, which is an extreme heatwave by UK standards.

Example 3: Telling an American friend the UK temperature

Inputs: Celsius: 15. Direction: C to F.

Fahrenheit = 15 x 9/5 + 32.
= 15 x 1.8 + 32.
= 27 + 32 = 59F.

Result: 15C equals 59F. A typical spring day in the UK.

Handy UK reference points: freezing = 0C (32F), a cold winter day = 5C (41F), a comfortable room = 20C (68F), a warm summer day = 25C (77F), a UK heatwave = 30C+ (86F+). For US oven temperatures: 300F = 149C, 325F = 163C, 350F = 177C, 375F = 191C, 400F = 204C, 425F = 218C, 450F = 232C. Body temperature is 37C (98.6F), and a fever typically starts at 38C (100.4F).