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Houseplant 101
Plant Calculators

Grow Light & DLI Calculator

Turn PPFD and hours-on into Daily Light Integral and check it’s enough.

in µmol/m²/s (from your light's specs)
per day (the photoperiod)

Is your grow light actually doing the job?

A bright-looking lamp can still leave a plant starved if it isn't on long enough, while a weak one left on all day can be plenty. DLI captures both at once. This tool converts your light's PPFD and run-time into a daily total, then checks it against typical targets.

Rough DLI targets for houseplants

  • Low-light plants: ~2-6 mol/m²/day
  • Medium foliage: ~6-12 mol/m²/day
  • High-light plants: ~12-20 mol/m²/day
  • Succulents & cacti: ~20+ mol/m²/day

Formula: DLI = PPFD × hours × 3600 ÷ 1,000,000.

Frequently Asked Questions

What is DLI (Daily Light Integral)?

DLI is the total amount of usable light a plant receives in one day, measured in moles of light per square metre per day (mol/m²/day). It combines how bright the light is (PPFD) with how long it’s on, which is a far better measure of "enough light" than brightness alone.

Where do I find my light’s PPFD?

Quality grow lights list PPFD (in µmol/m²/s) at a given distance in their specs or manual. If yours doesn’t, a PAR meter or a phone PAR app gives a rough reading. Remember PPFD drops quickly as you move the light further from the plant.

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