there are resources to do it for you, but really it's important to get the concept of % - makes life easier.
First, total up all your weights (in the same units, so all ounces or all grams or whatever). Then take each component and divide it by the total. Multiply by 100 and you have youer %.
For example
Coconut oil: 12 ounces
Olive oil: 10 ounces
Shea butter: 2 ounces
Total weight would be 24 0unces (12 + 10 + 2).
To figure out the % coconut oil, you simply divide 12 by 24 and get 0.50. Multiply by 100 (or move the decimal 2 places to the left) and you have 50. So your coconut oil is 50% of the mix.
Same procedure with the olive: 10 divided by 24 = 0.417. Round it to 0.42. Then multiply by 100 and you have 41.7%
Shea: 2 divided by 24 = 0.083. Multiply by 100 to get 8.3%
All your components together should = 100%
Coconut: 50%
Olive: 41.7%
Shea: 8.3%
All added together... 100%!
easy peasy.