That gives a dew point of about 74.1 °F, which is oppressive: sweat barely evaporates and hard exercise outside is risky.
How the dew point calculator works
DewPointCalc uses the Magnus formula with the Alduchov and Eskridge constants a = 17.625 and b = 243.04 °C. With the air temperature T in °C and relative humidity RH, it computes γ = ln(RH/100) + a·T/(b + T), and the dew point is b·γ/(a − γ). Going the other way, RH = 100·exp(a·Td/(b + Td) − a·T/(b + T)). Absolute humidity comes from the saturation vapour pressure, 6.112·exp(17.67·T/(T + 243.5)) hPa, times RH × 2.1674 divided by the temperature in kelvin. A surface at or below the dew point gets condensation; for painting, keep it at least 5 °F (3 °C) above.
Dew point comfort chart
| Dew point | Feels | Notes |
|---|---|---|
| Below 40 °F (4 °C) | Very dry | dry skin and static are likely, especially indoors |
| 40–54 °F | Comfortable | pleasant for most people |
| 55–59 °F | Slightly humid | still comfortable for most, a little sticky for some |
| 60–64 °F | Humid | sticky; most people notice the moisture |
| 65–69 °F | Muggy | uncomfortable, sweat evaporates slowly |
| 70–74 °F | Oppressive | very uncomfortable; take care with exercise |
| 75 °F (24 °C) and up | Miserable | dangerous for strenuous activity |
Dew point at 70 °F by humidity
| Relative humidity | Dew point |
|---|---|
| 20% | 27.1 °F |
| 30% | 37.1 °F |
| 40% | 44.6 °F |
| 50% | 50.5 °F |
| 60% | 55.5 °F |
| 70% | 59.8 °F |
| 80% | 63.5 °F |
| 90% | 66.9 °F |
Frequently asked questions
What dew point is comfortable?
Below about 55 °F (13 °C) most people feel comfortable; 60 °F (16 °C) and up starts to feel humid.
What is a high dew point?
Above 70 °F (21 °C) is oppressive, and 75 °F (24 °C) or higher is tropical and miserable for most people.
Why does a dew point of 50 feel fine at 90 °F?
The relative humidity is low, so sweat evaporates quickly and cools you even though it is hot.
Is DewPointCalc free?
Yes, with no sign-up or ads, and your readings stay in your browser.
How accurate is the result?
The formula is accurate to about 0.4 °C; most home hygrometers are only accurate to 2–5% RH, which matters more.