Temperature Converter: Quick Mental Math Cheat Sheet for Celsius, Fahrenheit, and Kelvin Conversions

Whether you are baking cookies from an American recipe at 350°F while your oven uses Celsius, checking whether 30°C requires a jacket (86°F — definitely beach weather), or running a science experiment that needs Kelvin, knowing how to convert between temperature scales is an essential everyday skill. Our Temperature Converter handles all conversions instantly, but understanding how the scales relate helps you estimate on the fly.

The Three Temperature Scales at a Glance

Scale	Used Where	Key Reference Point
Fahrenheit (°F)	United States, Bahamas, Cayman Islands	Water freezes at 32°F, boils at 212°F
Celsius (°C)	Most of the world	Water freezes at 0°C, boils at 100°C
Kelvin (K)	Science and engineering globally	0 K = absolute zero (−273.15°C)

Quick Mental Math Cheat Sheet

No converter handy? These shortcuts will get you within 1–2 degrees for everyday temperatures:

• F to C (rough): Subtract 30, divide by 2. Example: 86°F → (86−30)/2 = 28°C (exact: 30°C)
• C to F (rough): Multiply by 2, add 30. Example: 20°C → (20×2)+30 = 70°F (exact: 68°F)
• Exact formulas: °C = (°F − 32) × 5/9. °F = (°C × 9/5) + 32. K = °C + 273.15.
• Freezing point trick: 0°C = 32°F. For every +10°C, add +18°F. So 10°C = 50°F (32+18), 20°C = 68°F (32+36).

Real-World Conversion Reference Table

Situation	°F	°C	What It Feels Like
Freezing outdoor temp	32°F	0°C	Ice on roads, wear a coat
Pleasant spring day	68°F	20°C	Light jacket, comfortable
Hot summer afternoon	86°F	30°C	Shorts and t-shirt weather
Heat wave	100°F	38°C	Stay hydrated, avoid midday sun
Normal body temp	98.6°F	37°C	Healthy human temperature
Freezer	0°F	−18°C	Food storage temperature
Room temperature	68–72°F	20–22°C	Comfortable indoor range

Common Cooking Temperature Conversions

Oven Setting	°F	°C (conventional)	°C (fan)	Gas Mark
Very slow	250°F	120°C	100°C	1/2
Slow/Low	300°F	150°C	130°C	2
Moderate	350°F	177°C	160°C	4
Hot	400°F	204°C	180°C	6
Very hot	450°F	232°C	210°C	8

For exact results every time, use the Temperature Converter. Enter any value in °F, °C, or K and get all three results at once.

Common Conversion Mistakes and How to Avoid Them

• Dividing by 5/9 instead of multiplying: Remember: °C = (°F−32) × 5/9. The × comes after subtracting 32.
• Forgetting the −32 step: Always subtract 32 from Fahrenheit first, then apply the ratio.
• Confusing Kelvin with Celsius: Kelvin has no degree symbol. Write “300 K” not “300°K”. Add 273.15 to °C to get K.
• Using the rough shortcut for baking: The mental math shortcut is only accurate to ±2°. Use the exact formula or the Temperature Converter for cooking.
• Neglecting negative temperatures: The shortcuts work for positive and negative temps, but double-check near zero — 10°F is not 25°C below 0!

Try the free Temperature Converter now →