There is no correct figure, and nobody authoritative publishes one. That is the honest answer, and it is worth saying before the guesses start.
Debrett's, which will tell you what to wear to a traditional wedding and how many minutes before the ceremony to arrive, gives no amount for a wedding present. Neither does any other etiquette authority in Britain. Every specific number you have seen, and the "cover your plate" rule, comes from a supplier survey or from another article quoting one. They are descriptions of what some people said they spent. They are not rules, and you are not failing one.
What determines the amount
Four things, roughly in order of weight.
How close you are. The only real driver. A sibling and a colleague are not attempting the same gesture, and no table of figures can encode that.
What attending is already costing you. This is the factor most guides ignore and most guests feel. Travel, a night or two of accommodation, an outfit, possibly childcare - a destination or country wedding can cost a guest several hundred pounds before any present is bought. That expenditure is part of your contribution to the day, whatever the gift budget lists say. A smaller present from someone who has crossed the country isn't mean.
Whether there is a list. A list solves the problem, because the couple have set the range themselves by what they put on it. Choose something at the level you are comfortable with and stop calculating.
What you can afford. Stated last because it should be the floor, not the target. No couple worth attending wants a guest in debt over their gift.
The rule that replaces a number
If you want one principle to carry instead of a figure: give what makes you feel glad to have given it, and not a pound more.
A present chosen under resentment reads as one, eventually. A present chosen gladly at half the price does not.
Money instead of a present
Increasingly common, particularly where couples already have a home, and entirely acceptable where the couple have asked for it. Any gift request should have arrived with the invitation, so follow what they said.
Where money has been given, it is acknowledged the same way as any other present - Debrett's treats presents and offers of money identically at the engagement stage, expecting both to be acknowledged in writing.
What not to do
- Do not try to price-match another guest. You do not know their circumstances and they are not a benchmark.
- Do not read the venue as an invoice. An expensive wedding is the couple's choice about their own budget, not a bill issued to guests.
- Do not go off-list to be memorable. The list is what they asked for; ignoring it to be original is a gift to yourself.
- Do not skip the card because the gift is generous. The card outlasts most presents and costs nothing.
If you cannot afford much at all
Go anyway, and give something small with a good card. Attendance is not a fee-paying arrangement, and the guest list was written by people who wanted those specific people in the room.
Something made or written - properly written, not dashed off - lands better at the bottom of a budget than a cheap version of an expensive object.
Related: wedding gift etiquette for the rest of the conventions, and what to write in the card.
The wider path: the wedding.
