Au pairs - How did you work out the hourly rate for any additional hours?

[MrsFogi]

What is the usual way to work out the hourly rate for hours an au pair does in addition to her usual hours. I'm thinking if she covers on days one of the dcs are ill or agrees to do days in the holidays or simply ends up working more hours than usual in a given week.
Do you simply take the weekly rate and divide it by the usual number of hours? Or do people pick an hourly rate on some other basis?

The additional hours should be more than her normal hourly rate. Logic behind this is; her normal hourly rate is low because she's getting food/accommodation etc. included. If she does extra hours she isn't getting any additional food or accommodation so the cash part of her payment must be higher.

The fairest way to work out what she should be paid is to look at what the going rate is in your area. I would say an au pair is 'more' than a teen babysitter, but 'less' than a nanny, so somewhere in the middle of those? It probably depends on the age of your children and what she needs to do as well e.g. if they're early teens and she just needs to be in the house with them I would pay less than if they're infant school aged and need to be actively looked after and entertained.

Have you asked her what shed think is acceptable too? My au pair is very flexible with us but if she's asked to babysit for someone else she charge £8 per hour.

I pay an extra £6/hour - but I round it up.

At least whatever the NMW for her age is.