Light Calculator questionable?


New Member
Sep 21, 2017
Nova Scotia
So am I understanding this correctly?

The calculator says that 12 x 5W Cree LEDs (I'm using Cree-XP-g2 to be specific) should be 10" above a 48wx12lx13h tank with 4" substrate to give me a PAR of 55.


However, the calculator assumes all these LEDs are on the same strip across the tank.

Given that 6 lights suspended 5" above this tank would give me similar PAR (according to this calculator)...

If I divide my lights between two fixtures @ 6 lights/rail, then I can space the fixtures so I have about 6" between the front lights and the back lights, at a height of 5" above the tank. This should give me some adequate level of "high" light that would be manageable with pressurized CO2 and minor dimming/raising to account for the overlapping light?


New Member
Mar 17, 2023
United kingdom
I'm going to create a dedicated thread for this and a form that will allow members to submit the data.

@VaughnH as you are the light master ;) could you please list all Requirements for the form.

Fixture Name
Fixture Size
No# of Bulbs
Distance at 6"
Distance at 12"


Once I have all this data I'll create a form.

Also I would like to point out that @fablau is the guy that does the the clever backend stuff on the LED Lighting Calculator :) I'm the guy for the frontend GUI stuff, my design and Fabs engine.

Hello. kinda new to led lighting... I have a 60x60 led light 36watts 10pcs connected, my question is what would be the total load in kva. thank you


New Member
Jan 30, 2022
Gemla Sweden
Different led diodes and lenses will give very different values.
You need the models of the different leds to calculate a proper value.
I did a calculation of my 66 gallon tank and got 43 PAR. I have measured 40 so the calculator is good at least for my tank.