Guides/Temperature conversion tricks

Temperature conversion tricks without a calculator

Exact conversion needs ×1.8 and ±32. For weather and rough oven sense, a few mental tricks get you close — then verify when precision matters.

Exact formulas (when you can compute)

• °F = °C × 9/5 + 32 (same as ×1.8 + 32)
• °C = (°F − 32) × 5/9

Full walkthrough:Celsius to Fahrenheit explained.

Mental tricks

1. °C → °F (approx): double the Celsius, then add 30. 20 °C → 40 + 30 = 70 °F (exact is 68 °F — close enough for “mild day”).
2. Slightly better: double, add 30, then subtract ~10% of the doubled value for a rough 1.8× feel — or just remember key anchors below.
3. °F → °C (approx): subtract 30, then halve. 68 °F → 38 → ~19 °C (exact 20 °C).
4. From 0 °C: every 5 °C ≈ 9 °F. So 10 °C ≈ 50 °F, 25 °C ≈ 77 °F.

Memory anchors

• 0 °C = 32 °F (freezing)
• 10 °C ≈ 50 °F
• 20 °C ≈ 68 °F (room)
• 37 °C ≈ 98.6 °F (body)
• 100 °C = 212 °F (boiling at sea level)
• 180 °C ≈ 356 °F (often “350 °F” oven)

Worked examples

1. Weather: 28 °C → double + 30 = 86 °F (exact 82.4 °F — trick runs a bit high in heat).
2. Travel: 50 °F → −30 ÷ 2 = 10 °C (exact).
3. Oven: recipe 350 °F → (350 − 32) × 5/9 ≈ 177 °C (often printed as 180 °C).

Common mistakes

• Treating double-and-add-30 as exact for lab or medical numbers.
• Forgetting ±32 when using the precise formula.
• Mixing Kelvin offsets with everyday °C/°F weather talk.

Convert exactly

Use theUnit ConverterTemperature tab. Broader units:metric ↔ imperial.