For the 10% Permethrin that is commonly found in stores, mix 1 oz of it to 16 oz of water. I use Martins to stay away from the petroleum distillates in the mixture.
Want to know my secret insect repellent for hunting? Go to Coop and get the Bonide Bed Bug spray. It is water based vs petroleum distillate based. You don't have to mix it. Absolute best stuff for using on your hunting clothes period.