Free humidity calculators
Interactive tools that turn measurements into decisions. No signup, no tracking scripts — everything runs in your browser.
Real-time
Live US humidity right now
Current outdoor relative humidity in every state, refreshing itself automatically. Hover a state, oropen the full map.
- Under 45%
- 45–60%
- 60–68%
- 68–72%
- Over 72%
- Under 35%
- 35–55%
- 55–70%
- 70–85%
- Over 85%
Live conditions from each state's largest city viaOpen-Meteo. Average annual figures: NOAA / Brettschneider 2018.
Dehumidifier Size Calculator
Room size + dampness level → recommended pint capacity, based on the AHAM sizing standard.
Live nowElectricity Cost Calculator
Estimate the monthly cost of running a dehumidifier from watts, hours, and your utility rate.
Live nowCondensation Risk Checker
Compare your dew point with window surface temperature to see when glass will sweat.
Live nowUS Humidity Map
Interactive heatmap of average relative humidity for all 50 states — how damp is your region?
Live nowDew Point Calculator
Temperature + humidity → dew point, absolute humidity, and how the air actually feels.
Live nowHeat Index Calculator
Temperature + humidity → the NWS "feels like" heat index and its official risk level.
Live nowWindow Condensation Calculator
Indoor + outdoor temp and window type → the highest humidity before your glass sweats.
Live nowRelative Humidity Calculator
Temperature + dew point → relative humidity and absolute humidity, via the Magnus formula.
Live nowHumidity Comfort Checker
Is your indoor RH in the EPA healthy zone? Enter your reading for an instant verdict.
Live nowMold Risk Calculator
Temperature + humidity → mold-growth risk band and roughly how fast mold can appear.
Live nowTemperature-Change Humidity Calculator
Heat or cool the same air and watch RH change — why winter air is dry and cold surfaces sweat.
Live nowAbsolute Humidity Calculator
Temperature + RH → real water content in g/m³, grains per pound, and g/kg.
Live nowMuggy Meter: 7-Day Forecast
Live 7-day mugginess forecast for your area, ranked by peak dew point. New!
Live nowShould I Open My Windows?
Compares indoor vs outdoor moisture to tell you if opening up will dry or dampen the room.
Live nowWinter Humidifier Setting
Outdoor temperature → the highest indoor humidity you can run without fogging the windows.
Live nowVPD Calculator
Vapor pressure deficit in kPa for grow rooms, with the ideal range by growth stage.
Live nowWet Bulb to Humidity
Dry-bulb + wet-bulb temperatures from a psychrometer → relative humidity and dew point.
Live nowFrost Point Calculator
Temperature + humidity → the frost point, and whether surfaces will dew up or ice over.
Live nowIdeal Humidity Guide
The best relative humidity for your home, nursery, wood, instruments, wine, and more.
Live nowHumidifier Size Calculator
Room size + how dry it is → the right humidifier: tabletop, console, or whole-house.
Live nowBathroom Exhaust Fan CFM
Bathroom dimensions → the fan size in CFM to clear shower steam (HVI rule).
Live nowAir Changes Per Hour (ACH)
Room size + fan CFM → air changes per hour vs the recommended ventilation rate.
Live nowEvaporative Cooler Calculator
Temp + humidity → how cool a swamp cooler can get the air (great in dry heat).
Live now