Conversion - Instantaneous PPFD to Integrated PPFD
Most light meters measure the instantaneous photosynthetic photon flux density in µmol m-2 s-1 and yet plant growth is determined by the integrated daily photosynthetic photon flux density in mol m-2 d-1.
Here is how to convert from µmol m-2 s-1 to mol m-2 d-1 when using electric lights.
There are 3600 seconds in an hour. If the electric light output is constant, the instantaneous PPFD can be added up (integrated) over an hour.
Therefore 1 µmol m-2 s-1 = 3600 µmol m-2 h-1.
This must be divided by a million (1,000,000) to convert from micromoles to moles: 3600 µmol m-2 h-1 = 0.0036 mol m-2 h-1.
If the electric lights are on continuously (24 hours), the hourly PPFD must be multiplied by 24 to get the daily PPFD: 0.0036 mol m-2 h-1 = 0.0864 mol m-2 d-1.
There are 86,400 seconds in a day (3600 x 24 hours) so the daily PPFD can be calculated directly from the instantaneous PPFD from the following equation: µmol m-2 s-1 multiplied by 86,400 and divided by 1,000,000 = mol m-2 d-1.
So: 1 µmol m-2 s-1 = 0.0864 mol m-2 d-1 with continuous light
These conversions are accurate only under electric lights. The integrated daily PPFD from sunlight changes during the day so a single measurement cannot be used to estimate daily PPFD.
Daily PPFD Reference Table
24-Hour Photoperiod
| Instantaneous PPFD (µmol m-2 s-1) | Daily PPFD (mol m-2 d-1) |
|---|---|
| 10 | 0.864 |
| 100 | 8.64 |
| 200 | 17.28 |
| 300 | 25.92 |
| *600 | *51.84 |
| 1000 | 86.40 |
| 2000 | 172.80 |
16-Hour Photoperiod
| Instantaneous PPFD (µmol m-2 s-1) | Daily PPFD (mol m-2 d-1) |
|---|---|
| 10 | 0.567 |
| 100 | 5.67 |
| 200 | 11.52 |
| 300 | 17.28 |
| 600 | 34.58 |
| *1000 | *57.60 |
| 2000 | 115.20 |
12-Hour Photoperiod
| Instantaneous PPFD (µmol m-2 s-1) | Daily PPFD (mol m-2 d-1) |
|---|---|
| 10 | 0.432 |
| 100 | 4.32 |
| 200 | 8.64 |
| 300 | 12.96 |
| 600 | 25.92 |
| 1000 | 43.20 |
| *1300 | *56.23 |
| 2000 | 86.40 |