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Short answer: potatoes, almost everywhere. They're usually the single highest-calorie crop per square metre of any commonly grown vegetable, with other starchy staples close behind. Crops grown mainly for flavour or nutrition -- tomatoes, peppers, lettuce -- give a fraction of the calories per square metre that a staple does. But the exact ranking shifts by climate zone, since a crop's real yield depends on how well it actually grows where you are, not just its calorie density on paper.
Calorie Density Isn't the Whole Story
Two numbers determine how many calories a crop delivers per square metre: how many calories it provides per kilogram, and how many kilograms it actually yields from that square metre. A crop can have modest calorie density but still win on this measure by producing a huge amount of bulk -- which is exactly what potatoes do. They're not the most calorie-dense food by weight, but they yield heavily enough per plant to come out on top almost everywhere.
This is also why a generic "best crop" list can mislead. A crop's real yield changes with climate -- the same potato variety planted in a long, warm growing season will out-yield the identical variety in a short, cool one. So while potatoes are the safe general answer, the precise ranking for your own zone can differ, and it's genuinely worth checking rather than assuming.
This site's calorie rankings tool ranks every crop the calculator models by actual calories per square metre, by zone -- a more reliable answer than a generic list.
Frequently Asked Questions
What crop gives the most calories per square metre?
Potatoes are usually the single highest-calorie crop per square metre of any commonly grown vegetable, with other starchy staples like sweet potato and some grains close behind -- vegetables grown mainly for flavour or nutrition, like tomatoes, lettuce or peppers, are far behind by comparison. The exact ranking shifts by climate zone, since yield per plant changes with growing conditions.
Does the highest-calorie crop change depending on climate zone?
Yes -- a crop's calorie yield per square metre depends on how well it actually grows in a given climate, so the top performer in a warm, long-season zone isn't necessarily the top performer in a short, cool-season one, even though the crop itself provides the same calories per kilogram everywhere.
Should I only grow the highest-calorie crops?
No -- a diet of nothing but the single highest-calorie crop would leave a household missing vitamins, minerals and dietary variety that no amount of one staple crop can provide, so calorie-dense crops should form the bulk of a growing plan alongside a real range of other vegetables, not replace them entirely.