Whether you are a UK traveller checking the weather in the US, an American cooking with a British recipe, or a student working through a science problem — knowing how to convert Celsius to Fahrenheit is one of those practical skills that comes up again and again.
This guide gives you the exact formula, two quick mental shortcuts, a full conversion chart for common temperatures, and answers to the most searched temperature questions — all in one place.
Want to skip the maths? Use our free Unit Converter for instant, accurate temperature conversions — no signup required.
The Celsius to Fahrenheit Formula
The exact formula to convert Celsius (°C) to Fahrenheit (°F) is:
°F = (°C × 9/5) + 32 Or written another way: °F = (°C × 1.8) + 32
Both versions give the same result. The formula multiplies your Celsius value by 1.8 (or 9/5), then adds 32.
Step-by-step example — converting 25°C to Fahrenheit:
Step 1: 25 × 1.8 = 45 Step 2: 45 + 32 = 77 Result: 25°C = 77°F
The Fahrenheit to Celsius Formula
To go the other direction — Fahrenheit to Celsius:
°C = (°F − 32) × 5/9
Step-by-step example — converting 98.6°F to Celsius:
Step 1: 98.6 − 32 = 66.6 Step 2: 66.6 × 5/9 = 37 Result: 98.6°F = 37°C (normal body temperature)
Two Quick Mental Shortcuts
The exact formula involves multiplying by 1.8 which is awkward to do in your head. Here are two shortcuts that are accurate enough for everyday use:
Shortcut 1 — Celsius to Fahrenheit
Double and add 30
°F ≈ (°C × 2) + 30
Example: 20°C → (20 × 2) + 30 = 70°F (actual: 68°F)
Accurate within 2–4°F for temperatures between −10°C and 35°C. Perfect for checking the weather.
Shortcut 2 — Fahrenheit to Celsius
Subtract 30 and halve
°C ≈ (°F − 30) ÷ 2
Example: 86°F → (86 − 30) ÷ 2 = 28°C (actual: 30°C)
Accurate enough for quick everyday estimates — not for precise scientific or cooking conversions.
Celsius to Fahrenheit Conversion Chart — Common Temperatures
Weather temperatures
| Celsius (°C) | Fahrenheit (°F) | What it feels like |
|---|---|---|
| -10°C | 14°F | Very cold — heavy winter coat needed |
| -5°C | 23°F | Freezing — ice and snow likely |
| 0°C | 32°F | Freezing point of water |
| 5°C | 41°F | Cold — coat essential |
| 10°C | 50°F | Chilly — typical UK autumn day |
| 15°C | 59°F | Cool — light jacket recommended |
| 20°C | 68°F | Comfortable room temperature |
| 25°C | 77°F | Warm — typical UK summer day |
| 30°C | 86°F | Hot — US summer, southern Europe |
| 35°C | 95°F | Very hot — heatwave conditions |
| 40°C | 104°F | Extreme heat |
Body temperature
| Celsius (°C) | Fahrenheit (°F) | Meaning |
|---|---|---|
| 35°C | 95°F | Hypothermia risk |
| 36.1–37.2°C | 97–99°F | Normal body temperature range |
| 37°C | 98.6°F | Average normal body temperature |
| 38°C | 100.4°F | Fever (UK NHS definition) |
| 39°C | 102.2°F | High fever |
| 40°C | 104°F | Very high fever — seek medical help |
Cooking temperatures
| Celsius (°C) | Fahrenheit (°F) | Use |
|---|---|---|
| 100°C | 212°F | Boiling point of water |
| 150°C | 302°F | Low oven |
| 180°C | 356°F | Moderate oven — standard baking |
| 200°C | 392°F | Hot oven |
| 220°C | 428°F | Very hot oven |
| 250°C | 482°F | Maximum oven temperature |
Quick Reference — Most Searched Conversions
| Celsius | Fahrenheit | Common context |
|---|---|---|
| 0°C | 32°F | Freezing point |
| 20°C | 68°F | Room temperature |
| 21°C | 69.8°F | Ideal home temperature |
| 25°C | 77°F | Warm summer day |
| 30°C | 86°F | Hot weather |
| 37°C | 98.6°F | Body temperature |
| 38°C | 100.4°F | Fever threshold |
| 100°C | 212°F | Boiling point |
| -40°C | -40°F | Where both scales are equal |
💡 Fun fact: −40° is the only temperature where Celsius and Fahrenheit give exactly the same reading. At this point both scales intersect — −40°C = −40°F.
Why Do the UK and US Use Different Temperature Scales?
The Celsius (or centigrade) scale was developed by Swedish astronomer Anders Celsius in 1742. It is based on two fixed points: 0°C (water freezes) and 100°C (water boils). It is the standard in the UK, Europe, and most of the world.
The Fahrenheit scale was developed by German physicist Daniel Gabriel Fahrenheit in 1724. It is primarily used in the United States and a small number of other countries. On the Fahrenheit scale, water freezes at 32°F and boils at 212°F.
The UK officially adopted Celsius for most uses in the 1970s, though Fahrenheit is still sometimes used informally — particularly by older generations for body temperature and some cooking contexts.
Celsius vs Fahrenheit — Scale Comparison
| Celsius | Fahrenheit | |
|---|---|---|
| Used in | UK, Europe, most of the world | US, some Caribbean nations |
| Freezing point of water | 0°C | 32°F |
| Boiling point of water | 100°C | 212°F |
| Normal body temperature | 37°C | 98.6°F |
| Comfortable room temp | 20–22°C | 68–72°F |
| Developed | 1742 (Anders Celsius) | 1724 (Daniel Fahrenheit) |
Convert Any Temperature Instantly
Rather than working through the formula every time, use our free Unit Converter to convert between Celsius and Fahrenheit in one click.
Frequently Asked Questions
What is the formula to convert Celsius to Fahrenheit?
The formula is °F = (°C × 9/5) + 32. Multiply your Celsius value by 1.8, then add 32. For example, 20°C × 1.8 = 36, plus 32 = 68°F.
What is 37 degrees Celsius in Fahrenheit?
37°C = 98.6°F. This is average normal human body temperature. A temperature of 38°C (100.4°F) or above is considered a fever by the NHS.
What is 100 degrees Celsius in Fahrenheit?
100°C = 212°F. This is the boiling point of water at sea level.
What is 30 degrees Celsius in Fahrenheit?
30°C = 86°F. This is a hot summer day — common in southern Europe and the southern United States.
What temperature is the same in both Celsius and Fahrenheit?
−40°. This is the only point where both scales read the same value: −40°C = −40°F.
What is a normal body temperature in Fahrenheit?
Normal body temperature is 98.6°F (37°C). A fever is generally defined as 100.4°F (38°C) or above.
What is 20 degrees Celsius in Fahrenheit?
20°C = 68°F — comfortable room temperature. This is the typical temperature recommended for living spaces in UK homes.
Is 72°F hot or cold?
72°F = 22.2°C — this is warm and comfortable, often described as ideal room temperature. It feels pleasant without needing heating or air conditioning.
Summary — Celsius to Fahrenheit at a Glance
| Formula | °F = (°C × 1.8) + 32 |
| Quick shortcut | (°C × 2) + 30 ≈ °F |
| Freezing point | 0°C = 32°F |
| Body temperature | 37°C = 98.6°F |
| Boiling point | 100°C = 212°F |
| Equal point | -40°C = -40°F |
Temperature conversion formulas are mathematically exact. All values in this guide are correct to standard precision. For cooking, science, or medical purposes, always use the exact formula rather than mental shortcuts.