Examples · Converters

Celsius to Fahrenheit Examples: 10 Conversions

Ten conversions, including the two that are not conversions at all — a difference and a kelvin shift.

6 min read Updated 2026-08-23 Checked by Aziza Smailovic

Celsius to Fahrenheit

Multiply by 9/5, then add 32. These first four celsius to fahrenheit examples are the reference points worth knowing.

1. 0 °Cworked example

0 × 1.8 = 0scale
0 + 32 = 32 °Fwater freezes

2. 25 °Cworked example

25 × 1.8 = 45scale
45 + 32 = 77 °Fa warm room

3. 37 °Cworked example

37 × 1.8 = 66.6scale
66.6 + 32 = 98.6 °Fbody temperature

4. 100 °Cworked example

100 × 1.8 + 32 = 212 °Fwater boils

Fahrenheit to Celsius

Undo the steps in reverse: subtract 32 first, then multiply by 5/9.

5. 68 °Fworked example

68 − 32 = 36undo the offset first
36 × 5⁄9 = 20 °Cthen the scaling

6. 98.6 °Fworked example

98.6 − 32 = 66.6subtract
66.6 × 5⁄9 = 37 °Cback to body temperature

Negatives and the crossover

7. −10 °Cworked example

−10 × 1.8 = −18scale, keeping the sign
−18 + 32 = 14 °Fstill above zero on that scale

8. −40 °Cworked example

−40 × 1.8 = −72scale
−72 + 32 = −40 °Fthe one point where they agree

Example 7 is worth noticing: a temperature below zero in Celsius is comfortably above zero in Fahrenheit, because the Fahrenheit zero sits far lower.

The two that are not ordinary conversions

9. A rise of 15 °C — how much in Fahrenheit?worked example

15 × 1.8 = 27 °Fa difference scales but does not shift
do NOT add 32there is no zero point to correct

10. 25 °C in kelvinworked example

25 + 273.15 = 298.15 Kkelvin shares the Celsius degree size

Nine is the one people get wrong most often. Adding 32 to a difference gives 59 °F, which would mean a 15-degree rise felt like a 59-degree rise.

The formula behind all ten

Every one of the worked examples above is the same conversion formula with a different number in it.

Direction	Formula	In words
C → F	F = C × 9/5 + 32	nine fifths, then add the offset
F → C	C = (F − 32) × 5/9	remove the offset, then five ninths
C → K	K = C + 273.15	no scaling at all

The nine fifths is the ratio of degree sizes and the 32 is the difference between the zeros. A negative temperature changes nothing about the method — the sign simply travels through both steps, as example 7 showed.

The mental estimate, and how wrong it is

Double the Celsius figure and add 30. It works because doubling approximates 1.8 and 30 approximates 32 — but both approximations err upward, so the estimate always runs high.

°C	Shortcut	True °F	Off by
10	50	50	0
25	80	77	+3
37	104	98.6	+5.4
100	230	212	+18

Fine for deciding what to wear, useless above about 30 °C, and never acceptable in marked work.

Questions about celsius to fahrenheit examples

What is 25 °C in Fahrenheit?

77 °F. Multiply by 1.8 to get 45, then add 32.

What is 98.6 °F in Celsius?

37 °C. Subtract 32 to get 66.6, then multiply by 5/9.

How do I convert a temperature difference?

Multiply by 9/5 only. A difference has no zero point to correct, so the 32 does not apply — a rise of 15 °C is a rise of 27 °F.

Is the double-and-add-30 shortcut accurate?

Only near 10 °C. It runs a few degrees high at room temperature and is out by 18 degrees at boiling point.