A keyhole garden should be 6 to 8 feet (about 2 meters) across and 2 to 3 feet tall, with a notch cut into one side so you can step in. The right keyhole garden size is set by your reach, not by how much room you have. You stand in that notch and need to touch the compost basket at the center, so the radius can never be longer than your arm. Picture the bed as a round wheel with a wedge cut out, and you standing in that wedge.
Think about it from the middle out. The basket sits in the center, and you have to reach it from the notch to add scraps and water. A bed wider than 8 feet puts that basket past your fingertips, and then you cannot feed it without stepping on the soil. So the keyhole garden dimensions stay tight on purpose, because every part of the bed has to stay within one arm's length of where you stand. A typical adult reaches about 2.5 to 3 feet, and the notch eats into that distance, so 8 feet across is close to the real limit for most people.
Each number does a job. The 6 to 8 foot width keeps the center within arm's reach from the notch, so you can tend the whole bed from one spot. The 2 to 3 foot height raises the soil to waist level, which means you weed and harvest without bending your back. That waist height matters more than people expect, because a bed too low forces you onto your knees and a bed too tall is hard to fill. The notch is about 2 feet (24 inches) wide, just enough room to step in and turn around without crushing the plants on either side.
The basket at the center is the part most people get wrong. It should be about 1.5 feet across and run a bit taller than the bed itself. You fill it with food scraps and kitchen waste, and water it like a funnel. Nutrients seep out into the soil around it, which is why the bed stays rich without much extra feeding. Build the basket from wire mesh or thin branches so air and water move through the sides freely. These figures come from the SDSU Extension and from Bob Vila's build guides, and they line up because the reach math is the same for everyone. No matter where you garden, your arm is about the same length, so the standard size holds up across climates and yards.
When you ask how wide keyhole garden beds can go, the honest answer is that bigger is not better here. A wider bed looks like more growing space, but it traps the center where you cannot reach it. You end up climbing onto the soil, which packs it down and defeats the whole raised design. Packed soil drains poorly and chokes roots, so the bed that looked generous on paper grows worse food. Stay at 8 feet or under and the bed works the way it should, with every plant inside one easy reach.
Want more room to grow? Build a second keyhole bed instead of stretching one too far. Two 6-foot beds give you far more usable soil than one 12-foot monster, and you can still reach every plant in both. The right keyhole garden size is the one you can tend from a single spot, so a second bed beats an oversized one every time. Keep each bed at waist height, keep the basket within arm's length, and your back and your harvest will both thank you for it.
Read the full article: Keyhole Garden: A Complete Beginner Guide
