Four pay frequencies, four different annual totals
UK employees are commonly paid weekly (52 times a year), fortnightly (26 times a year), four-weekly (13 times a year), or monthly (12 times a year). Knowing which one you're on matters for budgeting, because these aren't interchangeable.
Why four-weekly pay isn't the same as monthly pay
A calendar year has 12 months but only fits 13 four-week periods, not 12, so four-weekly pay doesn't line up with calendar months. If you're paid four-weekly, you'll get 13 payments across the year rather than 12, which means two calendar months each year contain two pay days instead of one. Someone budgeting for a "regular" single payment every month can be caught out in those months, and can also be caught out assuming a bigger monthly figure than they actually average across the year.
Weekly pay has a similar effect
The same pattern applies to weekly pay: 52 weeks don't divide evenly into 12 months, so most years include a small number of months with an extra weekly payment in them.
Converting to a genuine monthly figure
To find your real average monthly income, annualise your pay first: weekly × 52, fortnightly × 26, four-weekly × 13, or monthly × 12, then divide the annual total by 12. This gives a consistent monthly figure regardless of how you're actually paid, rather than just using your most recent payment as a stand-in for "a typical month". See how to build a monthly budget for the full method and a worked example.
Use this alongside your budget
The Budget Planner applies this same annualise-then-divide approach automatically for every income and expense line, whatever frequency each one occurs at. You don't need to convert anything by hand. If you're converting between an hourly rate and a salary rather than a pay frequency, see the Hourly Wage Calculator instead.