Temperature conversions for weather, ovens and food safety
Temperature is the one conversion you can't shortcut with a single multiplier, because the scales don't share a zero point — 0°C and 0°F are completely different amounts of heat. The tool above handles Celsius, Fahrenheit and Kelvin (plus two historical scales) instantly in both directions. Below are the formulas it uses, the temperatures that actually matter in daily life, and the oven and food-safety charts that are the most common reasons people convert temperature at all.
The exact formulas
- Celsius to Fahrenheit: °F = (°C × 9/5) + 32
- Fahrenheit to Celsius: °C = (°F − 32) × 5/9
- Celsius to Kelvin: K = °C + 273.15
- Kelvin to Celsius: °C = K − 273.15
What the three main scales actually are
- Celsius (°C): The global everyday scale. Set by Anders Celsius in 1742, it anchors on the freezing (0°C) and boiling (100°C) points of water at sea level.
- Fahrenheit (°F): Used in the US and a few small territories. Set by Daniel Fahrenheit in 1724, it puts water's freezing point at 32°F and boiling at 212°F — exactly 180 degrees apart, which is why °F is "finer-grained" than °C for weather.
- Kelvin (K): The SI base unit, used in science. It starts at absolute zero (0 K = −273.15°C), the theoretical point of zero thermal energy.
Two rarer scales are included for completeness: Rankine (°R), an absolute scale using Fahrenheit-sized degrees, and Réaumur (°Re), where water freezes at 0° and boils at 80° — common in 18th-century Europe.
Milestones worth memorising
| Milestone | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | −273.15°C | −459.67°F | 0 K |
| Water freezes | 0°C | 32°F | 273.15 K |
| Room temperature | ~21°C | ~70°F | ~294 K |
| Normal body temperature | 37°C | 98.6°F | 310.15 K |
| Water boils (sea level) | 100°C | 212°F | 373.15 K |
Oven temperature chart
Recipes from different countries quote different scales, and fan (convection) ovens run hotter than conventional ones — the usual rule is to set a fan oven about 20°C lower. Here are the standard settings:
| Conventional °C | Fan °C | Fahrenheit | Gas Mark | Description |
|---|---|---|---|---|
| 140°C | 120°C | 275°F | 1 | Very slow / cool |
| 150°C | 130°C | 300°F | 2 | Slow |
| 170°C | 150°C | 325°F | 3 | Moderately slow |
| 180°C | 160°C | 350°F | 4 | Moderate (most baking) |
| 190°C | 170°C | 375°F | 5 | Moderately hot |
| 200°C | 180°C | 400°F | 6 | Hot |
| 220°C | 200°C | 425°F | 7 | Hot (roasting) |
| 230°C | 210°C | 450°F | 8 | Very hot |
Safe internal temperatures for meat (USDA)
A meat thermometer reading in one scale is the other common reason to convert. These are the widely used safe minimums:
| Food | °C | °F |
|---|---|---|
| Whole poultry & ground poultry | 74°C | 165°F |
| Ground meat (beef, pork, lamb) | 71°C | 160°F |
| Beef, pork, lamb steaks/roasts | 63°C + 3 min rest | 145°F + 3 min rest |
| Fish | 63°C | 145°F |
| Egg dishes | 71°C | 160°F |
Temperature questions that keep coming up
Is there a temperature where Celsius and Fahrenheit are equal?
Yes — exactly −40 degrees. −40°C equals −40°F. It is the only point where the two scales agree.
Why doesn't Kelvin use the degree symbol?
Because Kelvin is an absolute scale that starts from true zero, not from an arbitrary anchor like water's freezing point. In scientific convention you write "300 K", not "300 °K".
How can I estimate Fahrenheit to Celsius in my head?
Subtract 30, then halve: 80°F → (80−30)÷2 = 25°C. The exact answer is 26.6°C, so the shortcut is good for weather, not for cooking. For cooking, use the tool.
Why do European and US ovens use different numbers?
Because the US sets ovens in °F, Europe in °C, and UK gas ovens in gas marks. All three point to the same heat — 180°C, 350°F and gas mark 4 are the same moderate oven.