Yes, periodic expenses should always get converted to monthly averages. You should add your periodic expenses to your monthly budget. Let’s say you spent $480 on your last holiday vacation. To plan for this year’s holiday travel, you will need to break down that amount into monthly amounts. To do so, take the holiday spending and divide it by 12. Add the $40 ($480 divided by 12) to your monthly budget as a holiday expense. Ideally, keep that money in a different account from your daily expenditure account, so you don’t end up using it.