Two things matter more than the amount:
- Regularity. A monthly standing order lets a charity plan, and costs it far less than repeatedly fundraising to win you back. Many charities value £5 a month more than £60 once.
- Gift Aid. If you are a UK taxpayer, ticking the declaration adds 25p per £1 at no cost to you, and higher-rate taxpayers can reclaim more through Self Assessment.
If you want a framework, some donors use a fixed percentage of income; others set an annual budget and split it between one national charity and one local one. Either beats deciding in the moment when an appeal reaches you.
See tax-efficient giving for the reliefs available.