When using Chia or Flax seeds the conversion is as follows:
1 egg = 1 tbsp of ground flax seed/Chia seed + 3 tbsp water
Let the mixture set in the fridge for 15 minutes, stir.
This forms a jelly-like substance.
I had pre-ground chia seeds.
If you have flax seeds or chia seeds that are whole, grind the seeds down (by hand, or with a food processor)