HOME · CALCULATOR
Dew Point and Condensation Calculator
Find the dew point of your room air and whether your windows or walls are cold enough to collect condensation.
Check condensation
Dew point at 68°F
| Humidity | Dew point |
|---|---|
| 30% | 35°F |
| 40% | 43°F |
| 50% | 49°F |
| 60% | 54°F |
| 70% | 58°F |
How the risk is judged
The dew point is calculated with the Magnus formula used in meteorology. If you enter a surface temperature, the result compares it directly with the dew point. Without one, the risk is based on how far the room temperature is above the dew point: within 9°F (5°C) is high and within 18°F (10°C) is worth watching. These bands are our own rule of thumb.
Reducing condensation
Run bathroom and kitchen fans, dry laundry outside or in a vented dryer, keep furniture a little away from cold outside walls, and use a dehumidifier in damp rooms.
Frequently asked questions
What is the dew point?
The temperature at which air can no longer hold its water vapor. When a window, wall or pipe is at or below the dew point of the room air, water condenses on it.
Why do my windows get wet in winter?
Glass is the coldest surface in most rooms. At 68°F and 50% humidity the dew point is about 49°F, so any window colder than that collects water. Lowering humidity or warming the glass stops it.
What indoor humidity should I aim for?
The U.S. EPA recommends keeping indoor humidity below 60%, ideally between 30% and 50%, to limit mold. In very cold weather you may need the lower end to keep windows dry.
More tools
Sources and last updated
- Dew point formula (Magnus): WMO training material, Humidity Part 1
- Indoor humidity: U.S. EPA, A Brief Guide to Mold, Moisture and Your Home
Last updated: · 한국어로 보기