Plant Light Calculator

Estimate PPFD, daily light integral, and recommended light hours for low-, medium-, and high-light indoor plants from fixture wattage and coverage area.

Last updated: 2026-03-16

Plant light calculator

Enter your values

Estimate fixture intensity, daily light integral, and the photoperiod needed for low-, medium-, or high-light houseplants.

Recommended Light Hours

Enter your fixture and shelf coverage to estimate PPFD and the photoperiod your plant likely needs.

Calculation History (0)

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Example calculations

Tap an example to prefill the calculator with sample values.

Monstera shelf

Medium light plant under a 36 W LED

A common indoor setup where the fixture is strong enough but photoperiod matters.

Result: Enough PPFD for a healthy medium-light plant with a 12-hour day

Low-light pothos

Small fluorescent setup over a wide shelf

A forgiving plant that can do well even when DLI is modest.

Result: Low-light target met with a relaxed photoperiod

High-light propagation

High-light plant under a stronger LED

A setup where dialing in the photoperiod keeps growth high without overcooking the canopy.

Result: High-light DLI with fewer hours thanks to stronger PPFD

Why hours and intensity both matter

Plants respond to total usable light over the course of a day, not just wattage or a fixture label. That is why the calculator converts your setup into both an approximate PPFD and a DLI target.

If the suggested photoperiod is extremely long, the fix usually is not more hours. It is a smaller coverage area, a stronger fixture, or a shorter distance to the canopy.

Plant light FAQs

Helpful context for reading PPFD and DLI estimates.

What is PPFD?

PPFD stands for photosynthetic photon flux density. It estimates how many useful light photons hit a square meter of canopy each second, which makes it more useful than raw wattage alone.

What is DLI?

DLI is daily light integral, or total light over a full day. It combines intensity and hours, which is why a lower-intensity fixture can still work if you run it long enough.

How accurate is a wattage-based PPFD estimate?

It is directional, not lab-grade. Real PPFD changes with fixture design, hanging height, reflector shape, and losses at the canopy, so treat this as a planning estimate rather than an exact measurement.

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Disclaimer

This calculator provides general estimates for hobby projects. Results may vary based on specific conditions, materials, and techniques.

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