Short answer: there's no single weight, because the real starting point is calories, not kilograms. An adult needs roughly the same annual calorie total no matter which staple supplies it -- but potato, wheat and rice each provide very different calories per kilogram, so the weight required differs by crop before climate is even considered. Add in that yield per plant varies enormously by zone, and a single "you need X kg" answer would be wrong for almost everyone who reads it.
Why Published "You Need X kg" Figures Are Usually Wrong
Search for "how much wheat do I need per person per year" and you'll find confident-sounding numbers -- usually a single figure in kilograms, presented as if it applies universally. It doesn't, for two separate reasons that stack on top of each other.
First, calorie density differs by crop. A kilogram of potato provides meaningfully fewer calories than a kilogram of wheat, because potato is mostly water by weight. So even starting from the same annual calorie target, the weight of potato needed and the weight of wheat needed to hit that target are two different numbers -- comparing them directly as if "a kilogram is a kilogram" misses the point entirely.
Second, and just as important: how much of a crop a given amount of seed actually produces depends heavily on your climate zone. The same wheat seed sown in a long, favourable growing season yields more grain than the identical seed sown in a short, marginal one. A published weight figure has to assume some climate to arrive at its number -- and unless that climate happens to be yours, the figure is wrong for your situation. This site's calculator starts from your household's real calorie need and your actual zone, and works out the real weight, seed quantity and land required for each staple crop you choose -- not a generic number borrowed from somewhere else's climate.
Frequently Asked Questions
How much potato, wheat or rice do I need per person per year?
There's no single universal weight, because the real starting point is calories, not kilograms -- an adult needs roughly the same annual calorie total whichever staple supplies it, but potato, wheat and rice each provide a different number of calories per kilogram, so the actual weight needed varies by crop, and the actual land and seed needed varies further still by how well that crop yields in your specific climate zone.
Why can't staple crop quantities just be looked up in a table?
Because yield -- how much a given amount of seed or seed potato actually produces -- depends heavily on climate zone, and a generic table has to either pick one climate (making it wrong for everyone else) or average across climates (making it inaccurate for everyone), so a real answer has to start from your own zone's yield figures, not a single published number.
Should I grow just one staple crop, or several?
Several is generally more resilient -- relying on a single staple crop means a single pest, disease or bad season can threaten a large share of a household's calories, while spreading staple growing across two or three different crops (for example potatoes and grain) reduces that risk, provided the zone can support more than one of them well.