Help with Calculations

Joyful

Can some one tell me the easy way to work out on a month by month basis how to add interest to an amount when I have the APR? All the calculators seem to ask you how many months you wish to pay over but this is open ended.

I loaned a family member money ( I know!) a few years ago and kept transferring it to 0 percent cards but it then went onto a 13% APR until I have now added it to a lifetime balance card. What I need to know is per £100 how much interest do I add on for each month it was on the 13% card? Once I now that calculation I will be able to also do it for the lifetime balance calc.

Thanks in advance.

bengalknights

Multiply the amount by 1.08% a month to get the interest figure.

So far £100 it would be £1.08

Then following amount 101.08 * 1.08 etc

Joyful

I thought I was thinking as it was too easy that I was making a mistake but you've just confirmed I was thinking along the right lines so thanks.