Terrarium Grow Light Wattage Calculator

Terrarium Grow Light Wattage

Plant lighting needs depend on the size of the enclosure and the light requirements of the species inside. Modern LED panels are rated by actual watts drawn, not the legacy “incandescent equivalent”. Always check the spec sheet.

One honest caveat about watts per gallon. Light is an area phenomenon, not a volume one. A tall narrow jar and a shallow wide tank can hold the same gallons and need completely different fixtures, because the one that matters is how much light lands on the leaves. Watts per gallon survives as a rule of thumb because it came over from the aquarium hobby and because most terrariums are roughly cube-shaped, and the height adjustment below patches the worst of the gap. If your enclosure is unusually tall or unusually shallow, treat the number here as a starting point and buy a fixture with a published PPFD figure.

Watts per gallon (LED draw, not equivalent watts):

For a 10-gallon enclosure with tropical foliage: 10-15 W LED.

Adjustments by terrarium height:

• Under 12 inches tall: standard wattage
• 12-18 inches: +20% (light decays inverse-square law)
• Over 18 inches: +40% or use a more focused / higher-PPFD fixture

Adjustments by glass type:

• Clear glass top: standard
• Mesh top: +20% (mesh absorbs/scatters light)
• Frosted glass: +30% (significant light loss)

PPFD vs. wattage: PPFD (Photosynthetic Photon Flux Density, measured in μmol/m²/s) is the better metric because it counts the photons actually reaching the plants, but it isn’t always listed for hobby fixtures. Watts is a useful proxy for budget LEDs. For premium fixtures with PPFD specs:

• Low-light: 50-100 PPFD
• Tropical: 150-300 PPFD
• Bromeliads and orchids: 200-400 PPFD
• High-light and carnivorous: 400-700 PPFD

Photoperiod recommendations:

• Tropical: 10-12 hours
• Carnivorous: 14-16 hours (long-day cycle)
• Succulents: 12-14 hours
• Bromeliads and orchids: 12-14 hours
• Mosses / ferns: 8-10 hours (low-intensity, indirect feel)

Common LED fixtures and their actual watts:

• Hygger 18W aquarium light: ~12 actual W output
• Sansi 30W bulb: ~30 actual W
• Mars Hydro TS 600: ~100 W actual
• Twinstar 360S: ~22 W actual

Always verify the actual draw from the spec sheet, not the inflated “equivalent” wattage.