If you just want to know what your savings account will be worth in 10 years at 3% interest, you’re probably best off just using one of the online calculators for calculating appreciation. 

However, if for some reason, you want to know how it’s calculated, here it is:

x(1+b)ⁿ

where:

x = original amount
b = interest (3% should be represented as .03)
n = number of years

I couldn’t find this anywhere on the web and since it’s the second time I’ve calculated it by hand, I thought I’d share.