Income tax calculator

TinyPomegranate

I really like the income tax calculator on this site. One way I haven't figured out how to use it is, if I work extra hours or get a bonus in a month, how to work out what my income might be in that month (including tax/NI/pension etc) without telling it I earn that amount across the whole year. Could someone please help me, either with how to input that to the calculator on this site, or does anyone know of another calculator that will do this for you?

Thanks.

Dazed_and_C0nfused

HMRC's own one for tax is simple to use for individual paydays.

http://payecalculator.hmrc.gov.uk/PAYE0.aspx