Terrarium Humidity Calculator

The most common methods are misting with a spray bottle, adding a fogger or mister, using a humid hide filled with moist sphagnum moss, or reducing ventilation. Live plants also transpire and raise humidity naturally. Misting is most effective in well-ventilated enclosures; foggers suit high-humidity tropical species.

Needs vary widely by species. Leopard geckos prefer 30 to 40% relative humidity (RH). Crested geckos need 60 to 80% RH. Ball pythons require 60 to 80% RH. Dart frogs and many tree frogs need 80 to 100% RH. Always verify requirements for your exact species from an authoritative herpetological source.

Evaporation rate depends on enclosure volume, ventilation, substrate type, and ambient temperature. A rough estimate is that 1 mL of water per 10 litres of enclosure volume raises humidity by approximately 1 to 3% RH depending on ventilation. This calculator gives a starting estimate; adjust based on actual hygrometer readings.

Relative humidity (RH%) is the ratio of actual water vapour in the air to the maximum the air can hold at that temperature, expressed as a percentage. Absolute humidity is the actual mass of water vapour per unit volume. Terrarium keepers use RH% because it is what hygrometers measure and what affects animal physiology.

Use a digital hygrometer placed in the breathing zone of the animal, not directly above a water bowl or misting spot. Calibrate your hygrometer using the salt test: saturated sodium chloride solution in a sealed container should read 75% RH. Replace cheap analogue gauges with a calibrated digital unit for accuracy.