How this is calculated
Each person is assigned a calorie figure for their age band and activity level, and the household total is multiplied by 365.
The diet mix splits that demand between the animals and the crops, then the storage allowance is added back on, because what you eat in February is less than what came in from the field in September.
Each crop group carries a calorie density in calories per square meter, worked out from the 2025 United States yield per acre and the USDA calorie content. Divide the calories wanted by that density and the answer is ground. Grazing runs on the animal unit: a 1,000 pound cow eating 26 pounds of dry forage a day, with a quarter of the standing crop counted as reaching her.
The calorie figures behind each person
These are the estimated calorie needs from Appendix 2 of the Dietary Guidelines for Americans, averaged across the ages inside each band, and across both sexes for teenagers and children. The underlying estimates are the Institute of Medicine energy requirement equations of 2002.
| Person | Sedentary | Moderately active | Active |
|---|---|---|---|
| Adult man, 19 to 50 | 2,400 | 2,600 | 2,900 |
| Adult woman, 19 to 50 | 1,800 | 2,000 | 2,300 |
| Teenager, 14 to 18 | 2,000 | 2,300 | 2,700 |
| Child, 4 to 13 | 1,450 | 1,700 | 1,900 |
Calories a day. The published table runs by single year to age 18 and in five-year bands after that; a 16-year-old boy who works outside is on 3,200 a day, an office-bound woman of 45 on 1,800, so the two ends of one household differ by nearly two to one.
WORKED EXAMPLE
Two adults and two children, moderately active: 2,600 + 2,000 + 1,700 + 1,700 = 8,000 calories a day, 2.92 million a year. Half is 1.46 million; the mixed diet puts 20% on the animals, leaving 1.168 million from crops, and the 20% storage allowance lifts it back to 1.46 million calories of crop.
Staples take 62%: 905,200 ÷ 2,790 = 324 m². Beans take 12% at 760 per square meter: 231 m². Vegetables take 26% at 1,436: 264 m². 819 m² of crop, a fifth of an acre.
Six hens eat 936 pounds of grain a year, which is 363 m² of corn ground. One animal unit needs 9,490 pounds of forage; on ground carrying 4,500 pounds an acre with a quarter harvestable, that is 8.44 acres. The pasture is forty-two times the garden.
Calories per square meter by crop
Yields are the 2025 United States averages from the NASS Crop Production 2025 Summary and Vegetables 2025 Summary; calorie densities are the USDA standard reference values for the raw edible portion.
| Crop | US yield 2025 | Calories per 100 g | Calories per m² | Area for a million calories |
|---|---|---|---|---|
| Corn for grain | 186.5 bu/acre | 365 | 4,273 | 234 m² / 2,519 sq ft |
| Potatoes | 460 cwt/acre | 77 | 3,970 | 252 m² / 2,711 sq ft |
| Onions, dry | 599.6 cwt/acre | 40 | 2,688 | 372 m² / 4,004 sq ft |
| Tomatoes | 1,006.6 cwt/acre | 18 | 2,031 | 492 m² / 5,300 sq ft |
| Sweet potatoes | 208.8 cwt/acre | 86 | 2,013 | 497 m² / 5,348 sq ft |
| Carrots | 437.7 cwt/acre | 41 | 2,011 | 497 m² / 5,351 sq ft |
| Sweet corn, in husk | 158.1 cwt/acre | 86 | 1,524 | 656 m² / 7,063 sq ft |
| Cabbage | 444.4 cwt/acre | 25 | 1,245 | 803 m² / 8,644 sq ft |
| Wheat, all | 53.3 bu/acre | 327 | 1,172 | 853 m² / 9,183 sq ft |
| Beets | 233.8 cwt/acre | 43 | 1,127 | 887 m² / 9,552 sq ft |
| Squash, on butternut calories | 171.7 cwt/acre | 45 | 866 | 1,155 m² / 12,429 sq ft |
| Dry edible beans | 2,012 lb/acre | 337 | 760 | 1,316 m² / 14,163 sq ft |
| Romaine lettuce | 361.2 cwt/acre | 17 | 688 | 1,453 m² / 15,640 sq ft |
| Pumpkins | 215.2 cwt/acre | 26 | 627 | 1,595 m² / 17,164 sq ft |
| Head lettuce | 343.3 cwt/acre | 14 | 539 | 1,856 m² / 19,981 sq ft |
| Broccoli | 110.0 cwt/acre | 34 | 419 | 2,386 m² / 25,677 sq ft |
| Green peas, in pod | 45.1 cwt/acre | 81 | 409 | 2,442 m² / 26,288 sq ft |
| Snap beans | 83.7 cwt/acre | 31 | 291 | 3,439 m² / 37,011 sq ft |
| Spinach | 101.6 cwt/acre | 23 | 262 | 3,818 m² / 41,096 sq ft |
One hundredweight is 100 pounds; one acre is 4,046.9 m². These are commercial, largely irrigated yields, which is why the calculator scales them down for shorter seasons and dry ground. Two rows flatter their crop: sweet corn is weighed in the husk and green peas in the pod, while the calorie figures are for the kernels and the shelled peas.
In field units: 460 cwt an acre is 46,000 pounds of potatoes, so the 60% of the worked example’s staple bed that is potatoes carries about 2,200 pounds of them.
In field units: 460 cwt an acre is 51.6 metric tons a hectare, so the 60% of the worked example’s staple bed that is potatoes carries about 1,000 kilograms of them.
Density and shelf life multiply
Two things stack up on the staple bed. The first is density: a potato is 77 calories per 100 grams and romaine is 17, and potatoes out-yield lettuce by weight as well, so the gap opens to six to one.
The second is the calendar. USDA Agriculture Handbook 66 gives quality potato tubers 2 to 12 months in store; no lettuce of any type keeps beyond four weeks at 0°C, and half that at 5°C.
Squash sits in between and is often oversold. The same handbook keeps a good Hubbard six months at 10 to 13°C, but puts butternut at two to three months, and notes that longer storage buys spoilage and shrinkage.
The fair comparison is therefore calories per square meter still edible in February. On that measure salad ground is a summer luxury and the staple bed is the pantry.
Storage and preservation losses
Nothing arrives in the kitchen at field weight. Roots shrink, squash rots at the stem, onions sprout, and anything canned or dried gives up water. The allowance is a dial on the calculator rather than a measurement, and 20% is a starting point to argue with once you have your own weights.
Conditions move it more than variety does, and the three staples want three different rooms. Agriculture Handbook 66 stores eating potatoes at 7 to 10°C in 95 to 99% humidity, Hubbard squash at 10 to 13°C in about 70%, and pungent dry onions at 0°C in 65 to 75%.
No single cellar is all three, which is why most places end up with a cellar, a dry shelf and a freezer. The food preservation comparison costs those routes against each other, and the food without power clock covers a freezer that stops.
What the animals actually need
Grazing land is where the acreage goes. Oklahoma State University Extension sets an animal unit at a 1,000 pound dry cow eating 26 pounds of dry forage a day, and counts only 25% of the standing crop as reaching the animal; the rest is trampled, fouled, eaten by something else or lost to decay.
| Animal | Animal unit equivalent | Dry forage lb/day | Acres at 4,500 lb standing crop | Acres at 6,360 lb standing crop |
|---|---|---|---|---|
| Cow, 1,000 lb | 1.0 | 26.0 | 8.4 | 6.0 |
| Cow, 1,100 to 1,200 lb | 1.1 | 28.6 | 9.3 | 6.6 |
| Steer, 700 lb | 0.8 | 20.8 | 6.7 | 4.8 |
| Ram, 250 lb | 0.34 | 8.8 | 2.9 | 2.0 |
| Ewe, 175 lb | 0.27 | 7.0 | 2.3 | 1.6 |
| Dairy goat, 120 lb | 0.2 | 5.2 | 1.7 | 1.2 |
Animal unit equivalents and daily dry matter demand from Oklahoma State University Extension NREM-2886, March 2017. Acres are a full year of grazing at 25% harvest efficiency. The 4,500 pound standing crop is the figure that fact sheet works its summary on and 6,360 pounds is the tallgrass prairie figure in its examples; both columns are 26 pounds a day over 365 days, or 9,490 pounds. The fact sheet also publishes a rounder animal unit year of 9,360 pounds, which is 26 pounds across twelve thirty-day months.
Milk is where grass pays best. NASS put United States production at 2,075 pounds per cow for July in Milk Production of 21 August 2026, and whole milk carries 61 calories per 100 grams, so one productive cow turns pasture into more food energy than a family can drink. Beef sits at the other end: the average federally inspected steer dressed at 955 pounds across 2025.
Water follows the animals. A lactating 900 pound beef cow drinks 16.9 gallons a day and 100 laying hens 5.6, both from NDSU Extension AS1763. Size the supply with the water catchment calculator and read the full per-animal table in the water numbers chart.
European yields per hectare
Eurostat publishes the same quantity in metric tons per hectare, and one metric ton per hectare is 0.1 kilograms per square meter, so the calorie arithmetic is identical.
| Country | Potatoes t/ha | Calories per m² | Wheat and spelt t/ha | Grain maize t/ha |
|---|---|---|---|---|
| Germany | 45.02 | 3,467 | 7.08 | 10.05 |
| France | 42.44 | 3,268 | 5.97 | 9.20 |
| Netherlands | 41.70 | 3,211 | 6.97 | 8.46 |
| Ireland | 39.62 | 3,051 | 8.14 | — |
| Sweden | 37.34 | 2,875 | 6.17 | 6.77 |
| Spain | 32.11 | 2,472 | 3.65 | 12.12 |
| Poland | 30.20 | 2,325 | — | 7.22 |
| Italy | 28.78 | 2,216 | 3.66 | 9.97 |
| Romania | 13.87 | 1,068 | 4.09 | 2.83 |
Eurostat crop production in standard humidity, 2024 harvest, table apro_cpsh1, yield in tons per hectare. Calories per square meter use the same 77 per 100 grams for potatoes. Poland reports no combined wheat-and-spelt line for 2024 and Ireland no grain maize.
Cross-reading: the United States potato average of 460 cwt per acre is 51.6 metric tons a hectare, above every European country in the table.
Cross-reading: the United States potato average of 460 cwt per acre is 51.6 metric tons a hectare, above every country in the table; Romania at 13.87 shows what unirrigated smallholder ground returns.
Germany grows three times what Romania grows, same crop, same year, on land that is not in a different climate zone. That measured spread is why the calculator scales its yields between 65 and 135% and reports the growing ground as a band, and why any single land figure should be read as the middle of one.
Most homesteads buy grain
Grain is the quiet exception in every self-sufficiency plan. Wheat returns about 1,170 calories per square meter against 3,970 for potatoes, so bread costs three times the ground, and then it must be cut, threshed, winnowed, dried and milled.
Chicken feed is the same problem wearing feathers. University of Minnesota Extension puts a six-pound laying hen at roughly three pounds of feed a week, so six hens eat 936 pounds a year, more grain than most households eat themselves. Buying it is the plan most working homesteads run.
The egg figure the calculator returns uses the NASS rate of lay, 79.4 eggs per 100 layers a day on 1 August 2026, which is 290 a bird a year. A backyard flock that molts, slows in winter and keeps its hens past their second year will not reach that.
Quick answers
How much land does it take to feed a family of four?
About 800 m² of cropped ground to grow half the calories on a mixed diet, plus 6 to 8.5 acres if one grazing animal is part of it.
How many calories does a square meter of garden produce?
Roughly 3,970 from potatoes, 760 from dry beans and 688 from romaine lettuce at 2025 United States average yields.
Why do potatoes beat lettuce for survival calories?
Six times the calories from the same ground, and 2 to 12 months in store against four weeks at best.
How much pasture does one cow need?
Between 6 and 8.5 acres for a full year on the two standing crops Oklahoma State works its examples on, and more on thinner ground.
Do homesteads really grow their own grain?
Most buy it. Grain takes three times the ground of potatoes and a threshing floor most places do not have.
Sources
- Calorie needs. Dietary Guidelines for Americans, Appendix 2, Table A2-1, estimated calorie needs per day by age, sex and physical activity level, sourced there to the Institute of Medicine dietary reference intakes for energy, 2002.
- Field crop yields. USDA NASS, Crop Production 2025 Summary, January 2026: corn for grain 186.5 bu/acre, all wheat 53.3 bu/acre, potatoes 460 cwt/acre, dry edible beans 2,012 lb/acre.
- Vegetable yields. USDA NASS, Vegetables 2025 Summary: sweet potatoes 208.8, cabbage 444.4, carrots 437.7, onions 599.6, squash 171.7, romaine 361.2 cwt per acre, all 2025.
- Calorie densities. USDA standard reference: potatoes 77, sweet potato 86, butternut squash 45, red kidney beans 337, hard red winter wheat 327, yellow corn grain 365, romaine 17, whole egg 143, whole milk 61 calories per 100 g.
- Storage life. USDA Agriculture Handbook 66, The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks: quality potatoes 2 to 12 months, Hubbard squash 6 months at 10 to 13°C, butternut 2 to 3 months at 10°C, pungent dry onions 6 to 9 months at 0°C, lettuce no more than four weeks.
- Forage and stocking. Oklahoma State University Extension NREM-2886, Stocking Rate Determination on Native Rangeland, March 2017: animal unit 1,000 lb dry cow, 26 lb dry forage a day, 25% harvest efficiency, standing crops of 4,500 and 6,360 lb per acre.
- Livestock output. USDA NASS Milk Production, 21 August 2026, 2,075 lb per cow in July; Chickens and Eggs, 24 August 2026, rate of lay 79.4 eggs per 100 layers a day on 1 August; Livestock Slaughter 2025 Summary, steer dressed weight 955 lb for 2025.
- Hen feed. University of Minnesota Extension, raising chickens for eggs: a six-pound hen will eat roughly three pounds of feed each week.
- Livestock water. NDSU Extension AS1763, April 2024: lactating 900 lb beef cow 16.9 gallons a day; poultry from University of Kentucky extension, 5.6 gallons per 100 layers.
- European yields. Eurostat, crop production in standard humidity (apro_cpsh1), 2024 harvest.
- Calculator settings. The diet splits, the 65 to 135% yield scaling, the storage allowance and the watering rate are settings on the calculator, shown on its face so they can be changed.
Go deeper
Water bites first: size the supply with the water catchment calculator before committing to an irrigated acre. If heating comes off the same parcel, the woodlot size calculator runs the identical arithmetic for firewood, and the two answers compete for the same ground. Then walk the land buying checklist and see how growing and storing fit together in food off the grid.