A general rule of thumb is to cover 2-3 times the seed's width.
So cool! Love that visual and I've never heard it described that way. Thank you, I will never forget that! Also, your greenhouse is pretty neat. We built a lean-to for storing wood, but made the roof with the clear corrugated plastic just like you have there. We're planning on enclosing it now that the wood has been used over the winter and making it a mini-greenhouse for starting seeds! Looking forward to more tutorials. Thanks!