Kitchen Temperatures, °F and °C: Thermometer Check, USDA Numbers and Candy Stages

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Opens on Chapter 21’s example: Rafe’s new thermometer reads 34°F in ice water.

1. Convert

Temperature

A difference of degrees

2. Thermometer check

Reads in ice water (°F)

Then it reads

3. Food left out

Out of the fridge at

Above 90°F?

4. Candy stages

My water boils at (°F) 212 at sea level

Enter your numbers, then press Work it out.

How it works

°C = (°F − 32) × 5/9 and °F = °C × 9/5 + 32. A change of 25°F is 25 × 5/9 ≈ 14°C: no 32, because the 32 only lines up the starting points. If a thermometer reads 34°F in ice water it reads 2° high; subtract 2 from every reading (and look for 167 to be sure of 165). The food-safety numbers are USDA’s, as published; when in doubt, follow the official page. Sugar-stage targets are from one widely used table (others stretch soft ball to 245°F); up high, lower each target by however far below 212°F your water boils.

From the book, Chapter 21. A fridge at 38°F is 3.3°C. A 25°F change is 14°C (treating it as a temperature gives −4°C, wrong). Rafe’s thermometer is 2° high: 167 means 165, so look for 167. The Danger Zone, 40–140°F, is 4.4°C to 60°C; a freezer at 0°F is −17.8°C; reheat to 165°F, 73.9°C. Food out at 6:15 is back in by 8:15 pm (7:15 pm above 90°F, 32°C). At 203°F boiling, soft ball moves to 226–231°F. Every chapter and its calculator →

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