Micronized works a little better since the particle size is smaller. Below is the chart:
Concentration of Sunscreens & SPF 
Low 
Moderate

High 
Ultra High

Titanium Dioxide 
<4 % 
8 % 
12 % 
20 % 
Titanium Dioxide, Micronized 
2 % 
4 % 
6 % 
10 % 
Zinc Oxide 
5 % 
10 % 
15 % 
25 % 
Zinc Oxide, Micronized 
3 % 
7.5 % 
12 % 
20 % 
Above is a chart that our supplier has provided us. We do not do any testing internally. You can use it as a guideline if you want to label your lip balm with a specific SPF number. In our recipe the titanium dioxide is 1% of the recipe, so that would be a 25 SPF.
How do
I convert a toiletry recipe to percentages?
Convert each ingredient into the same measure, i.e: all teaspoons, all ounces,
all grams, etc. Add up and get the total of all of the ingredients. Take the
amount of each ingredient and divide by the total and then multiply by 100 to
get the percentage of each ingredient in the recipe.
Example Recipe:
9 tsps
beeswax
6 tsps cocoa butter
9 tsps shea butter
12 tsps avocado oil
2 tsps flavor oil
.5 tsps titanium dioxide white
1 tsp tocopherols
____
39.5 tsps total
9 tsps divided by 39.5 x 100 = 23 % of beeswax. And so on...