Fahrenheit → Celsius (America to Rest-of-the-World Mode)
Subtract 30 from the Fahrenheit temperature.
Cut the result in half.
Example:
86°F → 86 − 30 = 56 → 56 ÷ 2 = 28°C.
Actual: 30°C. We’re just 2 degrees off, which is good enough unless you’re cooking delicate French pastries.
Celsius → Fahrenheit (Rest-of-the-World to America Mode)
Double the Celsius temperature.
Add 30.
Example:
25°C → 25 × 2 = 50 → 50 + 30 = 80°F.
Actual: 77°F. Again, close enough to decide if you need shorts or a sweater.
Why It Works
The real formula uses 32 instead of 30 and a slightly awkward multiplication factor of 9/5 instead of 2. That simple. Hope it helps.