No EO should be used in more than a 3% dilution rate, strong eo's are anywhere from 0.5% to 2%, and these are adult rates. Children and the elderly are 1-2% for normal eo's, depending upon the eo and the age of the child. You can and should look at the IFRA dot org site to find the rates for specific essential oils, as many of the vendor sites do not supply accurate numbers.
ETA: also remember that the rate varies for each product type too. There are 10 categories and you must check them to find the appropriate usage rate.
Also, above I said that you shouldn't use an eo in more than a 3% dilution rate, but the wording is off and incorrect anyway. Some eo's, in some products can be used in higher percentages. Aromatherapists generalize that you need a 3% eo at max, but in other products many can be used at 5%. So you really need to know the product category and check the IFRA usage rates for each and every eo you want to use. If you are using more than one eo in a blend, you will need to check all numbers and carefully calculate each portion.