-40 Celsius to Fahrenheit (°C to °F) – Instant & Accurate
Last updated: February 28, 2026
-40 °C = -40.00 °F
Using the formula °F = °C × 9⁄5 + 32: -40 × 9⁄5 + 32 = -40.00 °F
How to convert from Celsius to Fahrenheit
It is easy to convert a temperature value from Celsius to Fahrenheit by using the formula below:
[°F] = [°C] × 9⁄5 + 32
or
Value in Fahrenheit = Value in Celsius × 9⁄5 + 32
To change -40° Celsius to Fahrenheit, just need to replace the value [°C] in the formula below and then do the math.
Step-by-step Solution:
-
Write down the formula: [°F] = [°C] × 9⁄5 + 32
-
Plug the value in the formula: -40 × 9⁄5 + 32
-
Multiply by 9: -360⁄5 + 32
-
Divide by 5: -72 + 32
-
Add 32: -40 (answer)
Nearby Conversions
Celsius to Fahrenheit Conversion Table (1–100 °C)
| Celsius | Fahrenheit | Celsius | Fahrenheit |
|---|---|---|---|
| 1 | 33.8 | 2 | 35.6 |
| 3 | 37.4 | 4 | 39.2 |
| 5 | 41.0 | 6 | 42.8 |
| 7 | 44.6 | 8 | 46.4 |
| 9 | 48.2 | 10 | 50.0 Cool day |
| 11 | 51.8 | 12 | 53.6 |
| 13 | 55.4 | 14 | 57.2 |
| 15 | 59.0 | 16 | 60.8 |
| 17 | 62.6 | 18 | 64.4 |
| 19 | 66.2 | 20 | 68.0 Room temperature |
| 21 | 69.8 | 22 | 71.6 Comfortable indoor |
| 23 | 73.4 | 24 | 75.2 |
| 25 | 77.0 | 26 | 78.8 |
| 27 | 80.6 | 28 | 82.4 |
| 29 | 84.2 | 30 | 86.0 |
| 31 | 87.8 | 32 | 89.6 |
| 33 | 91.4 | 34 | 93.2 |
| 35 | 95.0 | 36 | 96.8 |
| 37 | 98.6 Body temperature | 38 | 100.4 Mild fever |
| 39 | 102.2 | 40 | 104.0 High fever |
| 41 | 105.8 | 42 | 107.6 |
| 43 | 109.4 | 44 | 111.2 |
| 45 | 113.0 | 46 | 114.8 |
| 47 | 116.6 | 48 | 118.4 |
| 49 | 120.2 | 50 | 122.0 |
| 51 | 123.8 | 52 | 125.6 |
| 53 | 127.4 | 54 | 129.2 |
| 55 | 131.0 | 56 | 132.8 |
| 57 | 134.6 | 58 | 136.4 |
| 59 | 138.2 | 60 | 140.0 |
| 61 | 141.8 | 62 | 143.6 |
| 63 | 145.4 | 64 | 147.2 |
| 65 | 149.0 | 66 | 150.8 |
| 67 | 152.6 | 68 | 154.4 |
| 69 | 156.2 | 70 | 158.0 |
| 71 | 159.8 | 72 | 161.6 |
| 73 | 163.4 | 74 | 165.2 |
| 75 | 167.0 | 76 | 168.8 |
| 77 | 170.6 | 78 | 172.4 |
| 79 | 174.2 | 80 | 176.0 |
| 81 | 177.8 | 82 | 179.6 |
| 83 | 181.4 | 84 | 183.2 |
| 85 | 185.0 | 86 | 186.8 |
| 87 | 188.6 | 88 | 190.4 |
| 89 | 192.2 | 90 | 194.0 |
| 91 | 195.8 | 92 | 197.6 |
| 93 | 199.4 | 94 | 201.2 |
| 95 | 203.0 | 96 | 204.8 |
| 97 | 206.6 | 98 | 208.4 |
| 99 | 210.2 | 100 | 212.0 Boiling point |
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Where Celsius Meets Fahrenheit
−40 is the unique temperature at which the Celsius and Fahrenheit scales read exactly the same value. This can be derived algebraically by setting °F = °C in the conversion formula °F = °C × 9/5 + 32, which solves to −40. This intersection point has practical significance in extreme-cold environments: it appears in Arctic and Antarctic weather reports, cryogenic transport specifications, and is used as a test condition in automotive cold-start standards (SAE J2711).
Learn why this is the only point where both scales meet: Celsius vs Fahrenheit.
Data Accuracy
Every conversion on this page uses double-precision floating-point arithmetic (IEEE 754), which provides at least 15 significant decimal digits of internal precision. Results are then rounded to one decimal place for display. The underlying formula — °F = °C × 9/5 + 32 — is the internationally defined relationship between the Celsius and Fahrenheit scales, consistent with the International Temperature Scale of 1990 (ITS-90).
About This Page
Content maintained by the CelsiusFahrenheit.co editorial team. All conversions follow the International Temperature Scale of 1990 (ITS-90) as defined by the Bureau International des Poids et Mesures (BIPM). Calculations use IEEE 754 double-precision arithmetic. Last reviewed: February 2026.