When you work part time you don't have the luxury of knowing your annual salary offhand. To figure out how much you will make in a year's time, you must determine how many hours per week you will work and calculate from there.

Add up the number of hours you work per week. If this number is not consistent, then add up the number of hours worked each week for the last month, and divide them by four. For example, if you worked 18 hours on Week 1, 16 on Week 2, 17 on Week 3 and 21 on Week 4, your average number of hours worked would be 18. Use your average number of hours worked for the past month for your weekly calculations.

Take the number of hours worked per week and multiply by your hourly wage. If you are paid £5 an hour and worked an average of 18 hours per week, then your average weekly earnings would be £93.

Figure out how many weeks you will work in a year. If you will be, for example, on vacation for a week, you will need to deduct the number of weeks you will miss from the 52 weeks in a year.

Multiply your weekly earnings by the number of weeks you will work in a year. If you make £93 per week and will work 51 hours in the next year, then your annual salary would be £4,773.

Repeat Steps 1 through 4 for any other part-time job you may hold. Figure your earnings from each job, and add them together to determine your annual salary from all part-time jobs.