40°F to Celsius = 4.4°C

Fahrenheit to Celsius conversion table
°F	°C	Reference point
−40	−40	Both scales read the same
−20	−28.89
0	−17.78	Freezer setting
10	−12.22
20	−6.67
32	0	Water freezes
40	4.44	Refrigerator limit
50	10
60	15.56
65	18.33
68	20	Room temperature
70	21.11
72	22.22
75	23.89
80	26.67
85	29.44
90	32.22
95	35
97	36.11
98	36.67
98.6	37	Traditional normal body temp
99	37.22
100	37.78
100.4	38	Fever threshold
101	38.33
102	38.89
103	39.44
104	40	High fever
110	43.33
120	48.89
145	62.78	Whole cuts of beef, pork (USDA)
160	71.11	Ground meat (USDA)
165	73.89	Poultry (USDA)
212	100	Water boils at sea level
250	121.11
300	148.89
325	162.78
350	176.67	Moderate oven
375	190.56
400	204.44
425	218.33
450	232.22
500	260

40 °F at a glance

Celsius: 4.44 °C
Exact fraction: 4 4/9 °C
Kelvin: 277.59 K
Rankine: 499.67 °R
Rounded: 4 °C
Quick estimate: 5 °C

How to convert 40 °F to Celsius

°C = (°F − 32) × 5/9
(40 − 32) × 5/9 = 8 × 5/9 = 40/9 = 4.44 °C

Subtract 32 first because the two scales put zero in different places, then multiply by 5/9 because a Fahrenheit degree is only 5/9 the size of a Celsius degree. 8 is not a multiple of 9, so the exact answer is the repeating decimal 4 4/9 °C.

Estimate it in your head

Subtract 30 and halve: (40 − 30) ÷ 2 = 5 °C. That is 0.6 degrees high, close enough to decide what to wear.

What 40 °F means

Refrigerator range. The FDA says refrigerators should run at 40 °F (4.4 °C) or colder, so 40 °F (4.44 °C) is right at the upper limit. Bacteria multiply quickly between 40 °F and 140 °F, the “danger zone.”
Dress for it. 40 °F calls for a warm jacket, especially with wind; the wind chill index applies at 50 °F and below.

Wind	Feels like	In °C	Note
10 mph	34 °F	1 °C	Dress in layers
20 mph	30 °F	−1 °C	Dress in layers
30 mph	28 °F	−2 °C	Dress in layers

Temperatures near 40 °F

Fahrenheit	Celsius	Kelvin
35 °F	1.67 °C	274.82 K
36 °F	2.22 °C	275.37 K
37 °F	2.78 °C	275.93 K
38 °F	3.33 °C	276.48 K
39 °F	3.89 °C	277.04 K
40 °F	4.44 °C	277.59 K
41 °F	5 °C	278.15 K
42 °F	5.56 °C	278.71 K
43 °F	6.11 °C	279.26 K
44 °F	6.67 °C	279.82 K
45 °F	7.22 °C	280.37 K

Going the other way: 4 °C in Fahrenheit is 39.2 °F.

Frequently asked questions

What is 40 °F in Celsius?

40 °F is 4.44 °C: subtract 32 (8) and multiply by 5/9.

Is 40 °F hot or cold?

40 °F is cold — above freezing, but coat weather.

How do you convert 40 °F to Celsius in your head?

Subtract 30 and divide by 2: (40 − 30) ÷ 2 = 5 °C, compared with the exact 4.44 °C.

What is 40 °F in Kelvin?

40 °F is 277.59 K. Convert to Celsius (4.44 °C) and add 273.15.

Need a different value? Use the Fahrenheit to Celsius converter, or browse the Fahrenheit to Celsius chart.

Sources: Wind chill and heat index use the US National Weather Service formulas. Health and food-safety thresholds are from the CDC, FDA, USDA, CPSC and US Department of Energy.

40 °F to °C

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