Daily Light Integral Calculator
Enter your light's PPFD (photosynthetic photon flux density) and the number of hours it runs per day to calculate Daily Light Integral (DLI).
Last updated: September 25, 2026
Frequently asked questions
What's the difference between PPFD and DLI?
PPFD (photosynthetic photon flux density) is an instantaneous rate - how much photosynthetically active light is hitting a surface at a given moment, in µmol/m²/second. DLI (Daily Light Integral) is the total accumulated amount of that light delivered over a full day, factoring in both intensity and duration, in mol/m²/day.
How do I find my light's PPFD?
PPFD is typically measured directly with a quantum PAR meter at the plant canopy height and position you're planning to use, since it varies with distance and position under a light source - some grow light manufacturers also publish PPFD maps or tables for specific mounting heights, which can serve as an estimate if you don't have a meter.
What DLI should I target for my plants?
It depends heavily on species, growth stage, and growing environment - low-light houseplants may thrive around 4-6 mol/m²/day, many leafy greens and herbs do well around 12-17, and high-light fruiting crops or cannabis flowering stage often target considerably higher, sometimes 30-45+ mol/m²/day. This calculator doesn't recommend a target since the appropriate value depends entirely on what you're growing - check species- or crop-specific guidance.
Can I use DLI to compare sunlight and grow lights?
Yes - DLI is a useful common unit for comparing total daily light delivery from any source, whether natural sunlight (which varies by season, latitude, and weather) or artificial grow lights (which you control directly via PPFD and photoperiod), letting you plan supplemental lighting to reach a target total.
If I lower my light's intensity, how should I adjust the photoperiod to keep the same DLI?
Since DLI scales with the product of PPFD and hours, reducing PPFD requires proportionally increasing photoperiod to reach the same DLI, and vice versa - for example, halving PPFD while doubling the light hours delivers approximately the same total DLI, though very long or very short photoperiods can affect plants in other ways beyond total light delivered.
Does higher DLI always mean better plant growth?
Not necessarily - plants have species- and stage-specific ranges where more light improves growth, but beyond a certain point additional DLI provides diminishing returns or can even cause light stress or photoinhibition if not matched with adequate CO2, nutrients, and temperature. There's no single universally 'better' DLI - appropriate targets are specific to what's being grown.