40°C to Fahrenheit = 104°F

Celsius to Fahrenheit conversion table
°C	°F	Reference point
−40	−40	Both scales read the same
−18	−0.4	Home freezer (about 0 °F)
−10	14
0	32	Water freezes
4	39.2	Refrigerator (40 °F or colder)
10	50
15	59
20	68	Comfortable room
22	71.6
25	77	Warm day
30	86	Hot day
35	95
37	98.6	Normal body temperature
38	100.4	Fever
40	104
50	122
60	140
74	165.2	Poultry cooked through (165 °F)
80	176
90	194
100	212	Water boils at sea level
120	248
140	284	Very low oven
150	302
160	320	Low oven
170	338
180	356	Moderate oven
190	374
200	392	Moderately hot oven
220	428	Hot oven
230	446
240	464	Very hot oven
250	482
260	500	Pizza / max home oven

40 °C at a glance

Fahrenheit: 104 °F
Kelvin: 313.15 K
Rankine: 563.67 °R
Rounded: 104 °F
Quick estimate: 110 °F
As a change (Δ): Δ40 °C = Δ72 °F

How to convert 40 °C to Fahrenheit

°F = °C × 9/5 + 32
40 × 1.8 = 72
72 + 32 = 104 °F

Multiply by 9/5 (1.8) because each Celsius degree spans 1.8 Fahrenheit degrees, then add 32 because water freezes at 32 °F rather than 0. Since 40 is a multiple of 5, the result is a whole number.

Estimate it in your head

Double it and add 30: 40 × 2 + 30 = 110 °F, which is 6 degrees high — good for weather, not for cooking or medicine.

Careful with temperature changes: a rise of 40 °C is a rise of 72 °F — multiply by 1.8 but do not add 32.

40 °C on a thermometer and in the weather

Hot tub limit. 40 °C (104 °F) is the maximum hot-tub water temperature the US Consumer Product Safety Commission recommends. As a body temperature it is a high fever that needs medical care.
As weather. An air temperature of 40 °C (104 °F) is an intense heat wave. Even in dry air, the heat index is high:

Relative humidity	Heat index	NWS category
10%	37 °C	Extreme caution
25%	41 °C	Danger
40%	48 °C	Danger

Temperatures near 40 °C

Celsius	Fahrenheit	Kelvin
35 °C	95 °F	308.15 K
36 °C	96.8 °F	309.15 K
37 °C	98.6 °F	310.15 K
38 °C	100.4 °F	311.15 K
39 °C	102.2 °F	312.15 K
40 °C	104 °F	313.15 K
41 °C	105.8 °F	314.15 K
42 °C	107.6 °F	315.15 K
43 °C	109.4 °F	316.15 K
44 °C	111.2 °F	317.15 K
45 °C	113 °F	318.15 K

Going the other way: 104 °F in Celsius is 40 °C.

Frequently asked questions

What is 40 °C in Fahrenheit?

40 °C is 104 °F: multiply by 1.8 (72) and add 32.

Is 40 °C hot or cold?

40 °C is around body temperature — a fever if it is your temperature, and a heat wave as weather.

How do you convert 40 °C to Fahrenheit quickly?

Double it and add 30: 110 °F. The exact value is 104 °F.

What is 40 °C in Kelvin?

Add 273.15: 40 °C = 313.15 K.

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

Sources: Wind chill and heat index use the US National Weather Service formulas; boiling points at altitude use the Antoine equation for water and the standard atmosphere. Health and food-safety thresholds are from the CDC, USDA, CPSC and US Department of Energy.

40 °C to °F

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