# Changing Percentages When Adding Ingredients To A Base

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#### rpclarke

##### Member
Hi,

I just want to make sure my maths is correct before labeling my products. If I have, say, 10kg of base for a lotion or cream, and add 2% of a new ingredient, would I do the following calculation?

10,000 / 0.98 = 10,204

And therefore add 204g of the new ingredient to make it 2%?

Would I also then need to adjust the percentage of the ingredients currently in the base? Because surely if, say, I added 50% of a new ingredient then all the other percentages would half?

I hope this makes sense and if I've got things wrong please let me know!

#### ResolvableOwl

##### Notorious Lyear
Yes, this is the correct way to calculate it.

With small additions, the difference between 200 g (2.00% added, 1.96% concentration in the final product) and 204 g (2.04% added, for 2.00% of the final product) is small, but it gets larger with higher percentages.

2% addition will also dilute everything in the base by these 2%. So if, say, X was 34.8% in the base, it then will be 34.8% × 0.98 = 34.1% afterwards.
And if you mix base + addition 1:1, X would go down to 17.4%.

If you want to be precise with concentration of several additives, you have to know the whole recipe beforehand, to dose fillers properly.

#### rpclarke

##### Member
Thank you for clarifying that, I really appreciate it!

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