Useful Excel percentage formulas

If A2 is the part and B2 is the total, use =A2/B2 and apply Percentage formatting. For old A2 and new B2, use =(B2-A2)/A2. To increase A2 by the percentage in B2, use =A2*(1+B2).

These formulas assume the referenced cells contain numeric values and that the denominator is not zero. The Excel percentage formula builder can generate the pattern.