A putt so short your opponent tells you to just pick it up — it counts as holed without being struck. Gimmes are legal in match play, where conceding a stroke is part of the rules, but never in stroke play, where every ball must reach the bottom of the cup. In casual golf they mostly exist to keep things moving. The informal yardstick is "inside the leather": closer to the hole than the length of your putter's grip, roughly 2 feet.
Source: https://www.usga.org/content/usga/home-page/rules/rules-2019/rules-of-golf/rule-3.html · high confidence
A putt so short your opponent tells you to just pick it up — it counts as holed without being struck. Gimmes are legal in match play, where conceding a stroke is part of the rules, but never in stroke play, where every ball must reach the bottom of the cup. In casual golf they mostly exist to keep things moving. The informal yardstick is "inside the leather": closer to the hole than the length of your putter's grip, roughly 2 feet.
Source: https://www.usga.org/content/usga/home-page/rules/rules-2019/rules-of-golf/rule-3.html · high confidence