The formula
gift = price per head × people going × closeness factor
Where it comes from
There is no rule about what you give at a wedding, but there is a reference that comes up everywhere: cover at least what your places cost, and go up from there with closeness. The logic is simple — a gift is not a payment, but it should not leave the couple paying for your seat either. Above that floor, what you add is what you think right and what you can afford, and that is where the range opens up. Which is why this page returns an interval: naming one exact figure would fake a precision that does not exist.
How to work it out by hand
- Find out or estimate what a place costs at that venue
- Multiply it by the number of you going on the invitation
- Apply the closeness factor: from one times the place for an acquaintance to two or three for immediate family
- If you are bringing a physical gift, take its value off the money
What is worth knowing
All of this is the custom around sit-down wedding receptions and does not transfer as it stands everywhere. There are two cases where the per-place reference does not apply: when there is a gift list or a honeymoon fund, where what you choose is the gift, and when there is no reception. And if the budget will not stretch, going and giving less is better than not going: nobody who invites you wants that to keep you away.