A full-size pitch is about 105 by 68 metres. That sentence does not produce a fixture count. Count comes from mast height, setback, beam angle, the wavelength the paint was built for, and the radiant flux of the actual head. Electrical watts are the power bill. They are not the UV on the grass.
Use the radiant-flux column
On the 496TG series the top model, GY496TG1600(8), draws 1600 W and is published at 559.1 / 727.5 W radiant flux for the two wavelength options. A 200 W module in the same family is 69.8 / 90.9 W radiant. Those pairs are third-party radiometric figures, and they are the inputs a lighting calculation should see.
Beam angle is the other lever. 60° is the tighter throw for a high mast. 120° is the wider wash for a lower side position or a shorter field. Mixing them without a drawing is how corners fall off.
What to send instead of guessing a number
Send the pitch or field dimensions, mast or roof height, voltage, and a note on the fluorescent system (line paint, uniforms, halftime set). We simulate the UV layout and return a coverage report. That service is free, and it replaces a fixture count invented from a rule of thumb.
If you need a starting shortlist before the drawing arrives: high masts point at 496TG, shorter stands and training grounds often land on 296TG or 35TG, and a touchline or tunnel that must also work in white light points at the dual-source line.
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Not sure how many fixtures your venue needs?
Send a floor plan or field dimensions. Our engineers simulate the UV layout and send a coverage report, free.