How to choose the right LED T8 tubes?

If you still have traditional TL tubes then the number of wattage is connected to the length of the tube. The higher the wattage, the longer the tube. So if you have a traditional 36 Watt fluorescent tube then you can replace it with for example a 120 cm - 18 Watt LED tube. If you have a traditional 58 Watt fluorescent tube you can replace it with a 150 cm - 22 Watt LED tube.

Note that you look at the number of lumens when purchasing a lamp, the higher the number of lumens, the more light output. It has nothing to do with wattage when you compare light output, the lower the wattage, the less energy it consumes. Keep in mind that you buy the same lumen value to have the same light output as your old TL tubes.