PPFD to DLI Calculator — Convert PPFD to Daily Light Integral
Convert PPFD to DLI in one step: DLI = PPFD × photoperiod (hours) × 0.0036. Solve in either direction — find the DLI a fixture delivers, or the PPFD or photoperiod needed to hit a target DLI — then check the result against DLI targets by crop and growth stage and estimate the lighting energy it costs.
How to Convert PPFD to DLI
The conversion is one multiplication: DLI = PPFD × photoperiod (hours) × 0.0036. For example, 400 µmol/m²/s over a 16-hour photoperiod gives 400 × 16 × 0.0036 = 23.0 mol/m²/day. The 0.0036 constant simply converts micromoles per second into moles per hour: there are 3,600 seconds in an hour and 1,000,000 micromoles in a mole, so 3600 / 1,000,000 = 0.0036. PPFD (Photosynthetic Photon Flux Density) is an instantaneous rate — how many photosynthetically active photons land on a square meter each second, in µmol/m²/s. DLI (Daily Light Integral) is the accumulated total those photons add up to over 24 hours, in mol/m²/day. PPFD is the flow rate; DLI is the volume in the tank at the end of the day, and DLI is the number that actually determines yield, quality, and morphology. Most leafy greens need 12–17 mol/m²/day, herbs 15–22, and fruiting crops 20–30. Exceeding the target wastes energy; falling short limits yield.
How to Use This Calculator
- 1 Choose your solve mode: convert PPFD to DLI, find the PPFD needed for a target DLI, or find the photoperiod for a target DLI.
- 2 Enter your known light parameters — PPFD in µmol/m²/s and photoperiod in hours. The calculator applies DLI = PPFD × hours × 0.0036 and solves for the missing variable in real time.
- 3 Select a crop and growth stage to compare your DLI against its optimal range.
- 4 Set your LED efficacy, electricity rate, and grow area to estimate lighting energy costs.
PPFD to DLI Chart (mol/m²/day)
Every value below is PPFD × hours × 0.0036. Find your PPFD down the left, your photoperiod across the top, and read the DLI. The conversions growers ask for most often are worked out in full below, each with its own anchor.
| PPFD (µmol/m²/s) | 12 h | 14 h | 16 h | 18 h | 20 h | 24 h |
|---|---|---|---|---|---|---|
| 100 | 4.3 | 5.0 | 5.8 | 6.5 | 7.2 | 8.6 |
| 150 | 6.5 | 7.6 | 8.6 | 9.7 | 10.8 | 13.0 |
| 200 | 8.6 | 10.1 | 11.5 | 13.0 | 14.4 | 17.3 |
| 250 | 10.8 | 12.6 | 14.4 | 16.2 | 18.0 | 21.6 |
| 300 | 13.0 | 15.1 | 17.3 | 19.4 | 21.6 | 25.9 |
| 400 | 17.3 | 20.2 | 23.0 | 25.9 | 28.8 | 34.6 |
| 500 | 21.6 | 25.2 | 28.8 | 32.4 | 36.0 | 43.2 |
| 600 | 25.9 | 30.2 | 34.6 | 38.9 | 43.2 | 51.8 |
| 700 | 30.2 | 35.3 | 40.3 | 45.4 | 50.4 | 60.5 |
| 800 | 34.6 | 40.3 | 46.1 | 51.8 | 57.6 | 69.1 |
| 900 | 38.9 | 45.4 | 51.8 | 58.3 | 64.8 | 77.8 |
| 1,000 | 43.2 | 50.4 | 57.6 | 64.8 | 72.0 | 86.4 |
| 1,200 | 51.8 | 60.5 | 69.1 | 77.8 | 86.4 | 103.7 |
Commercial CEA produce sits in roughly the 12–30 mol/m²/day band, which is why 200–600 µmol/m²/s at a 16–18 hour photoperiod covers almost every leafy green, herb, and fruiting crop grown indoors. The higher PPFD rows are included because the arithmetic is asked for, not because leafy greens can use that much light — above a crop’s saturation point the extra photons cost energy and return nothing.
Worked PPFD to DLI Conversions
The full arithmetic for the conversions growers ask for most often, at the two most common commercial photoperiods.
- 300 PPFD to DLI
- 300 × 16 × 0.0036 = 17.3 mol/m²/day at a 16-hour photoperiod, or 300 × 18 × 0.0036 = 19.4 mol/m²/day at 18 hours. A 16-hour day at 300 µmol/m²/s lands squarely in the butterhead and romaine target band.
- 400 PPFD to DLI
- 400 × 16 × 0.0036 = 23.0 mol/m²/day at a 16-hour photoperiod, or 400 × 18 × 0.0036 = 25.9 mol/m²/day at 18 hours. That is above the lettuce band and into strawberry and tomato territory; running lettuce here wastes energy and invites tip burn.
- 500 PPFD to DLI
- 500 × 16 × 0.0036 = 28.8 mol/m²/day at a 16-hour photoperiod, or 500 × 18 × 0.0036 = 32.4 mol/m²/day at 18 hours. Appropriate for fruiting crops at their light-hungry stages, well past saturation for leafy greens.
- 600 PPFD to DLI
- 600 × 16 × 0.0036 = 34.6 mol/m²/day at a 16-hour photoperiod, or 600 × 18 × 0.0036 = 38.9 mol/m²/day at 18 hours. Above the published range for every crop in the table below — worth checking the PAR meter reading before acting on it.
- 800 PPFD to DLI
- 800 × 16 × 0.0036 = 46.1 mol/m²/day at a 16-hour photoperiod, or 800 × 18 × 0.0036 = 51.8 mol/m²/day at 18 hours. At this intensity CO₂ enrichment and transpiration capacity, not photons, become the limit on what the crop can convert.
- 1000 PPFD to DLI
- 1,000 × 16 × 0.0036 = 57.6 mol/m²/day at a 16-hour photoperiod, or 1,000 × 18 × 0.0036 = 64.8 mol/m²/day at 18 hours. Roughly double what any produce crop in commercial CEA can use.
Reverse the formula to solve the other way: PPFD = DLI ÷ (hours × 0.0036), and photoperiod = DLI ÷ (PPFD × 0.0036). To hit 16 mol/m²/day over 16 hours, for instance, you need 16 ÷ (16 × 0.0036) = 278 µmol/m²/s.
DLI Targets by Crop & Growth Stage (mol/m²/day)
Once you have converted PPFD to DLI, this is what to compare it against. Ranges are for sole-source LED lighting in a sealed or semi-sealed indoor environment.
| Crop | Overall Range | Propagation | Grow-out / Veg | Harvest / Fruit |
|---|---|---|---|---|
| Butterhead | 12–17 | 8–10 | 14–17 | 14–17 |
| Romaine | 14–18 | 8–10 | 15–18 | 15–18 |
| Leaf Lettuce | 12–16 | 8–10 | 13–16 | 13–16 |
| Basil | 15–22 | 8–12 | 18–22 | 18–22 |
| Arugula | 12–16 | 8–10 | 12–16 | 12–16 |
| Kale | 14–20 | 8–10 | 16–20 | 16–20 |
| Microgreens | 8–14 | 0 (blackout) | 10–14 | 10–14 |
| Strawberry | 18–26 | 14–18 | 20–24 | 22–26 |
| Tomato | 20–30 | 15–18 | 22–28 | 25–30 |
| Cucumber | 18–28 | 14–18 | 20–25 | 22–28 |
Light is only half the picture: the same DLI produces a different result depending on whether the crop can transpire. Check the matching humidity target on the VPD calculator or the printable VPD chart, and the full climate, CO₂, EC and pH set for each of these crops on the optimal growing conditions reference.
Frequently Asked Questions
How do I convert PPFD to DLI?
Multiply PPFD by the photoperiod in hours, then by 0.0036: DLI = PPFD × hours × 0.0036. For example, 400 µmol/m²/s for 16 hours = 400 × 16 × 0.0036 = 23.0 mol/m²/day. The constant comes from unit conversion alone — 3,600 seconds per hour divided by 1,000,000 micromoles per mole.
What is the PPFD to DLI formula?
DLI = PPFD × photoperiod (hours) × 0.0036, where PPFD is in µmol/m²/s and DLI is in mol/m²/day. Written out in full it is DLI = PPFD × hours × 3600 / 1,000,000. Rearranged, PPFD = DLI ÷ (hours × 0.0036) and photoperiod = DLI ÷ (PPFD × 0.0036).
What is the difference between PPFD and DLI?
PPFD (Photosynthetic Photon Flux Density) measures the instantaneous intensity of photosynthetically active light in µmol/m²/s — like measuring water pressure from a hose. DLI measures the total accumulated light over 24 hours in mol/m²/day — like measuring total gallons delivered. Two farms can have the same DLI with different PPFD and photoperiod combinations.
How much DLI does lettuce need?
Most lettuce varieties perform best at 12–17 mol/m²/day during grow-out. Butterhead is on the lower end (12–17), while romaine needs slightly more (14–18) for dense heart formation. During propagation, 8–10 mol/m²/day is sufficient. Exceeding 20 mol/m²/day for lettuce wastes energy and can cause tip burn. At a 16-hour photoperiod, 16 mol/m²/day works out to 278 µmol/m²/s at the canopy.
What LED efficacy should I use?
Budget LED fixtures run around 2.0 µmol/J, mid-range around 2.5, premium around 2.8, and top-shelf fixtures exceed 3.2 µmol/J. Higher efficacy means less electricity per mol of light delivered. Check your fixture spec sheet for the PPE (Photosynthetic Photon Efficacy) rating.
Does higher DLI always mean higher yield?
Not necessarily. Each crop has a saturation point beyond which additional light provides diminishing returns or causes stress (tip burn, bolting, bleaching). The goal is to hit the optimal DLI range for your crop and stage — not to maximize it. The energy cost of the last 10% of DLI often exceeds the yield benefit.
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