Converting F-to-C, C-to-F

If you just want a simple numerical answer, use

A Converter-Calculator (for F-to-C and C-to-F)

But if you want to UNDERSTAND the two scales,

and two ways to convert from F to C, and C to F, by

using a** mathematical equation **or** visualizing-and-memory**.

A convenient starting
point for conversions is to

compare the boiling and freezing points of water:

BOILING POINT of water is | 100° C | 212° F |

difference in degrees = | 100 C° | 180 F° |

FREEZING POINT of water is | 0° C | 32° F |

As you can see by comparing numbers in the table above,

degrees** differ in SIZE:** 100 C° = 180 F°, so **5
C° = 9 F°**

(a Celsius-degree is larger than a Fahrenheit-degree, and

there are **100** C-degrees between freezing and boiling, so

the Celsius scale originally was called the **Centi**grade scale)

The two scales also** differ in STARTING POINTS:** I find it useful to

think in terms of the freezing point of water, at **0° C = 32°
F** .

To convert between temperatures in °C and °F, calculate how

many degrees the temp is above (or below) freezing water,

and then add (or subtract) this from either 0°C or 32° F, so

temperature in °F = 32 + (9/5)(0 - °C)

You can use the formulas above to convert by math-calculating, but for practical everyday conversions

I think it's more useful to

(to understand-and-remember more easily) you can begin at 0/32 and move upward or downward:

°C | °F |

etc | etc |

40 | 104 |

35 |
95 |

30 | 86 |

25 |
77 |

20 | 68 |

15 | 59 |

10 |
50 |

5 | 41 |

0 | 32 |

- 5 | 23 |

-10 | 14 |

-15 |
5 |

-20 | - 4 |

-25 | -13 |

-30 | -22 |

-35 | -31 |

-40 |
-40 |

etc | etc |

continues above and below the temperature range in the table.

To interpolate between these 5-and-9 temperatures, you can

estimate that temperature changes by 1 C° for every 2 F°.

And for more precision, use the easy calculations below;

to make the math more intuitive and easy to remember,

we'll start at 10-and-50 where both temps end in a "0":

°C | °F | °F | °F |
°C |

10 | 50 + 0/5 | 50.00 | 50 |
10 |

11 | 50 + 9/5 | 51.80 | 52 |
11 |

12 | 50 + 18/5 | 53.60 | 54 |
12 |

13 | 50 + 27/5 | 55.40 | 55 |
13 |

14 | 50 + 36/5 | 57.20 | 57 |
14 |

15 | 50 + 45/5 | 59.00 | 59 |
15 |

each interval (except the middle) is 2, for 22122.

10 | 11 | 12 | 13 | 14 | 15 | |||||

50 | 52 | 54 | 55 | 57 | 59 | |||||

+2 |
+2 |
+1 |
+2 |
+2 |
the differences are 2 2 1 2 2 |

Or, to estimate temperatures in the reverse direction, notice

the pattern of paired temperatures (

in-between Celsius temperatures, but not for temperatures that are multiples of 5, such as 10 and 15.

°F | °C + C° | °C | °C |
°F |

50 | 10 + 0/9 | 10.00 | 10 |
50 |

51 | 10 + 5/9 | 10.56 | 11 |
51 |

52 | 10 + 10/9 | 11.11 | 11 |
52 |

53 | 10 + 15/9 | 11.67 | 12 |
53 |

54 | 10 + 20/9 | 12.22 | 12 |
54 |

55 | 10 + 25/9 | 12.78 | 13 |
55 |

56 | 10 + 30/9 | 13.33 | 13 |
56 |

57 | 10 + 35/9 | 13.89 | 14 |
57 |

58 | 10 + 40/9 | 14.44 | 14 |
58 |

59 | 10 + 45/9 | 15.00 | 15 |
59 |

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