Enter the PPF or Photon Efficiency

In order to calculate efficiency, coverage and harvest potential we need to use Photosynthetic Photon Flux (PPF) data. If you have a light fixture in mind, look for PPF or Photon Efficiency (PPE) data in the manufacturer’s literature or on their website. Manufacturers of high efficiency lights will usually report this data because it is a selling point. For most grow lights, PPF values are between 100 and 1500 µmol. Photon efficiency values are usually between 1.00 and 3.00 µmol/w.

PPF (Not PPFD)

PPF values are often called “PAR Value” or “Total PAR”. They measure the total amount of Photosynthetically Active Radiation (PAR) that a fixture will produce. This data will be reported as “µmol” or “µmol/s”. You can enter this data in the Grow Light Calculator in the field labeled “µmol”.

Unfortunately, many manufacturers of low-quality lights do not report PPF data. They instead try to manipulate Photosynthetic Photon Flux Density (PPFD) data to convince growers that the lights are more powerful than they are. PPFD is a measure of the density rather than the quantity of photons. The data reported in PAR maps is PPFD data. PPFD values are properly reported as µmol/m²/s. If you see the “m²” in the label, then it is PPFD data which cannot be used in the Grow Light Calculator.

Use Photon Efficiency Data

It is more common to find a Photon Efficiency rating. Photon Efficiency is often abbreviated as “PPE”. It is a number usually between 1.00 µmol/w and 3.00 µmol/w. The label may say µmol/w or µmol/j, there is no difference. We can use photon efficiency ratings instead of PPF values in the calculator.

Photon Efficiency is simply the PPF divided by the power draw. Enter this value into the field labeled “µmol/w”. The calculator will multiply the photon efficiency by the number of watts to estimate the PPF in µmol.

Read more about Grow Light Metrics in our Grow Light Metrics Primer.

Select Calculated, Total or Usable PPF

There are three ways that PPF values are measured or calculated. PPF values may be a “Calculated PPF”, or they may be measurements of “Total PPF” or “Usable PPF”. In our grow light calculator, you can select which type of PPF data that you want to input. The default is set to “Calculated PPF” because this is the data that most manufacturers provide. If you click on the drop-down menu, you can select Total PPF or Usable PPF.

If you are using manufacturer’s data, you should assume that it is a calculated value. This is most obvious when the PPF data that they report is directly related to the efficiency of the LED diodes that they use. Several manufacturers of high-end LEDs publish data from lab testing. You should select “Total PPF” if you are using data from lab testing. The data from our field test reports are Usable PPF values, however manufacturers generally do not publish Usable PPF data.

When you select “Calculated PPF” or “Total PPF”, we use our formulas to estimate the Usable PPF. When you select “Usable PPF” we do not make any adjustments. The calculator will report the new PPF value as the “Estimated Usable PPF”. All other calculations for efficiency, coverage and harvest potential are then based on the Estimated Usable PPF.

Read about the science behind our formulas in our article, “Calculating Grow Light Efficiency, Coverage & Harvest Potential”.

Questions about the Grow Light Calculator?

If you have questions about the metrics and what they mean, please see our Grow Light Metrics Primer. If you have questions about how to use the calculator or our calculations, efficiency ratings, or formulas, please see our article, “Calculating Grow Light Efficiency, Coverage & Harvest Potential”. If you want to learn about our grow light testing procedures, check out our Grow Light Testing Protocol.

Still have questions, or want to discuss? Start a thread in our Grower’s Forum or come chat with us in our Live Cannabis Chatroom!