Can someone explain interest rates please?

Greenstuff_2

I am so sorry, I know I should know this but I really can't figure it out.
I have 2 credit cards that I am tarting, but due to circumstances I have let them lapse ( I know, slap me round the back of the head with my money diet).
I have sent for new cards to 0% them, but the bills have have both arrived this morning with interest on them.
One is Marbles, o/s balance £4,368.78 current monthly interest rate 1.313% (15.8%pa) 16.9% APR interest charged £32.42
The other is Amex, o/s balance £3,794.96 interest rate 1.46% (it doesn't have the others) interest charged £57.44.
The interest on the Amex is almost double the Marbles, but I can't figure out why, I need to know this stuff in case I get in this position again, can someone please explain? Simple terms would be greatly appreciated!
Thanks
Victoria

dthyer

The Marbles figure looks like about 17 days worth of interest. Maybe the 0% offer ended part way between the previous statement and the one you just got?
Marbles one month's interest = £4368.78 * 0.01313 = £57.36
£57.36 * 17/30 = £32.50

The Amex figure looks like a full month of interest maybe slightly more, but sometimes the gap between statements can be more than a month to avoid statment dates falling on non-banking dates (e.g. Saturday or Sunday).
Amex on month's interest £3794.96 * 0.0146 = £55.41
£55.41 * 31/30 = £57.25

N.B. In both the above calculations I assumed that a month is a 'nominal' 30 days, whereas they may use a more precise figure e.g. 365/12 or something like that, which might explain the few pence difference.

I hope this helps,

DT

Greenstuff_2

Dt, thanks, that explains it perfectly.

Simple when you know how, how clever you are.

dthyer

8) I just like doing sums. Glad it helped.