Why Field & Farm Calc?
Most of these answers live buried in university extension PDFs, decades-old forum threads, and the back of a feed-store brochure. We turned the published formulas into clean, fast calculators that work on your phone — in the barn, in the woods, or on the water. Every tool shows its math and cites its sources, so you can trust the number and double-check it too.
What's here, and when you'd reach for it
Feeding the herd through winter. The hay calculator turns head count, body weight and days of feeding into bales, including the feeding waste that most back-of-the-envelope estimates leave out — and waste is not a rounding error, since the difference between a bale ring and rolling hay out on the ground can be a fifth of the crop. Once you know how many tons you need, hay prices shows what hay is actually trading for by state and quality grade, pulled from USDA Agricultural Marketing Service market reports with the report name and date on every row, so you can tell whether the load in the classified ad is priced fairly.
Managing pasture. Three tools cover one subject at three different time scales. Stocking rate is the season-long question: how many head the whole place carries between green-up and dormancy. Paddock calculator is the layout question: how many paddocks a given rest period needs, and how big each one should be. Grazing days is the everyday question: how long the herd can stay where they are before they should move. All three run on the same published forage figures from the University of Kentucky grazing stick tables and the same rotation identity from West Virginia University Extension, so their answers agree with each other.
Getting application rates right. Spreader calibration uses Penn State Extension's tarp method to tell you what your manure spreader is actually putting down per acre — which is almost never what the spec plate implies, because the plate is a volume figure and manure's weight per cubic foot swings with bedding and moisture. Drill calibration does the same for seed, using a catch test that is checked against Penn State's own worked example. Both exist because equipment drifts and rate charts were written for different seed, in a different condition, years ago.
Land and lease decisions. Cash rent reports USDA National Agricultural Statistics Service survey values for cropland and pasture by state, pulled from the QuickStats database rather than from someone's recollection. Hunting lease shows published state lease-rate surveys as ranges with the survey year attached, deliberately never averaged together, because a 2001 Kansas survey and a 2023 Missouri survey are two different facts rather than two samples of the same one.
Heat and firewood. Heat cost converts wood, propane, natural gas, heating oil and electricity into the one unit that lets them be compared — dollars per million Btu delivered into the room — using Utah State's species heat values and standard energy constants, with appliance efficiency applied exactly once. Firewood estimates how many cords a winter takes for your house and climate.
Ponds, fish and deer. Pond calculator handles volume, surface acres and the treatment math that depends on them. Fish weight estimates weight from length by species, so a fish can go back in the water without a scale. Food plots sizes seed and fertilizer for the acreage you actually have, including the pure-live-seed conversion that bag tags require. Rut timing maps peak breeding dates by state from wildlife agency studies, most of them based on fetal measurement, with the states that have no published study listed honestly as having none.
How these are built
Every formula on this site traces to a published extension-service, university or federal-agency source, named on the page where the number is used and dated. Every calculator has an automated test that re-implements its math independently, and where the source authority publishes a worked example, that example is the test — so the page is checked against the extension service's answer, not against itself. Nothing deploys unless the whole suite passes.
Everything runs in your browser. Nothing you type is sent anywhere, there is no account, and there is no app to install. These are planning estimates built from published averages and ranges, and rural averages have wide spread — for decisions where being wrong is expensive, your county extension office, veterinarian or state fisheries biologist can see your ground in a way a calculator cannot. More on the sourcing, the testing and the review schedule is on the about page.