How to Work out a % variance for negative numbers

Hi, I know that the following question is probably very simple to you guys and girls but it is causing me a bit of trouble.
I am preparing budget to actual varinances as a % these are very simple when both number are positive, but I am struggling to know what formula I need to use to work out if the numbers are negative for example if I had a budgeted loss of -£10,000 but actually made a loss of -£5,000 the percentage will tell me that % performance of the unit was only 50% but actually they were better than they budgeted for?
If i had a budget of £5000 and and actual of £10,000 then the % perfomance is above 100 so would assume that a negative equivilant would be the same?
Can anyone help as I seem to be confusing myself the more I think about it?
Regards
Martin

The variance is the average of , where is the mean. It really doesn't matter whether the numbers are positive or negative.