You can calculate with percentages and to get percentages using excel.
To find out a percentage value of a number it is a simple multiply. For example if you want to find out what 10% of 35 is the calculation would be:
= 35 * 10%
When you use the percent symbol Excel knows what you are inputting. 10% is 0.1 and because you are multiplying by less than 1 the answer is a smaller number than the original.
If you want to find out what an increase of 10% is to 35 then the calculation would be:
= 35 * 10% + 35
This takes the original 10% value and adds it to the original amount of 35.
You can also calculate what percentage an amount is compared to another amount. If we look at the example of our budget is 5000, so far this year we have reached 4799, what percent have we reached?
= ( 4799 * 100 / 5000 ) * 0.1
Do you have a calculation you use for percentage?