What this is
BaleMath is a collection of free, single-purpose calculators for hay, barn, water, and manure planning. Each one answers a question people otherwise work out on the back of a feed-store receipt: how much hay the animals need before the pasture comes back, how much barn floor a winter's stack will take, whether the round bales down the road really beat the squares in town once waste is counted, or how much water and manure a winter plan must handle. There are no accounts, no apps, and no spreadsheet to maintain. Every tool is a single page that works the moment it loads.
The main hay calculator covers the common species in one place, with dedicated versions for horses, goats, and cattle. Alongside them sit a hay storage space planner, a price converter for weighing a per-bale offer against a per-ton one, a round versus square comparison that totals a full winter's cost with waste included, a winter livestock water planner, and a manure output calculator.
Who makes BaleMath
BaleMath is built and maintained by Valentijn — one person, not a company. I made it because winter feed planning is the sort of thing people work out on the back of a feed-store receipt, and getting it a little wrong means either running short in February or paying for hay that rots in the barn. Every number here traces to a named university-extension source (listed further down), and the tools stay free and account-free on purpose. If a figure looks off, a source needs updating, or you just have a question, email contact.balemath@gmail.com — corrections are genuinely welcome.
The method, in plain English
The hay calculators start from the same rule: a mature animal at maintenance eats a fairly steady share of its body weight in forage each day. For a horse that is about 2 to 2.5 percent — 20 to 25 pounds of hay a day for a 1,000-pound animal — and closer to 3 percent in hard cold. Beef cows run near 2 percent at maintenance and about 2.5 percent in winter, goats around 3 percent, sheep about 2 percent, alpacas and llamas 1.5 to 2 percent. Donkeys are the common surprise: Cornell Cooperative Extension puts their voluntary intake at just 1.3 to 1.8 percent, well below the horse figures many owners borrow.
One caveat worth naming plainly: the horse and pony figures are as-fed — pounds of hay as it comes off the stack — which is the convention University of Maryland and Penn State use. Several of the ruminant, camelid, and donkey figures, though, are published by their sources as dry-matter intake. Because baled hay is only about 85 to 92 percent dry matter, the equivalent as-fed amount is roughly ten percent higher. We apply the published percentages directly as an honest planning simplification, so for those species treat the base daily figure as a floor rather than a ceiling. The storage and feeding-waste buffers layered on top absorb most of that gap in practice — but if your hay is damp, or you simply want a cushion, round up.
The hay tools multiply that daily need across the herd and the days without pasture to get a base tonnage. Storage loss and feeding waste are applied on top, the total is divided by bale weight — about 50 pounds for a small two-string square, about 900 for a typical round — and the bale count rounds up, because nobody sells two-thirds of a bale.
The other tools keep the same visible-input approach. The price converter normalises each offer to price per pound and per ton. The storage planner converts bale count and entered bale weight to tons, applies Missouri Extension's 250-cubic-feet-per-ton square or 310-cubic-feet-per-ton round storage rate, and divides by usable stack height. Its headline does not automatically add site-specific aisles or clearances. The water planner multiplies each livestock group by its published daily rate before applying reserve days and an outage margin. The manure tool scales UMass Extension's daily output rates by animal weight and head count, then applies collection days and bedding.
The catch: the hay you buy is not the hay they eat
Homemade estimates run short for one reason more than any other: they skip the losses. Storage comes first. Hay kept inside a barn loses about 5 percent of its dry matter, per University of Maryland and N.C. Cooperative Extension figures. Stored outside but covered or up on pallets, the loss runs around 15 percent; left outside on bare ground uncovered, about 30 percent over 12 to 18 months, per Mississippi State University Extension's storage-loss tables. Then comes feeding waste. N.C. Cooperative Extension puts it at roughly 13 percent for square bales fed on the ground — a figure Penn State also uses — 5 percent from a hay rack, and 3 percent from a basket feeder. Round bales are harsher still: research summarized by Nutrena and the University of Minnesota reports losses up to 57 percent with no feeder at all, and 5 to 33 percent with one; the calculators default to 19 percent, the midpoint of that range.
Skipping those two steps is how a "four months of hay" purchase runs out in February, and February is the wrong month to be buying. Hay is generally cheapest right after summer cutting and most expensive in late winter. We do not publish price forecasts; for real prices, check your local listings or the USDA AMS hay reports.
Where the sourced numbers come from
One version-controlled data file supplies the shared planning assumptions used by the hay, storage, water, and manure tools; the price converter uses only the offer values entered by the visitor. Each confirmed constant traces to a named source below, nearly all of them university-extension publications. Values without a confirmed primary source are marked for verification and presented as estimates.
| Topic | Sources |
|---|---|
| Horse intake & waste | University of Maryland Extension, "Calculating Your Horse's Winter Hay Needs"; Penn State Extension, "Buying Winter Hay for Horses"; N.C. Cooperative Extension, "Calculating Winter Hay Needs"; Mad Barn; Nutrena / University of Minnesota (K. Martinson, PhD), "Estimating Winter Hay Needs" |
| Beef cattle intake | University of Wisconsin–Madison Division of Extension; University of Nebraska–Lincoln (UNL Beef); Ohio State University Extension; North Dakota State University Extension; University of Florida IFAS Extension |
| Goat intake | University of Nebraska–Lincoln Extension (G2267); Alabama Cooperative Extension System; UF/IFAS Extension (Duval County); Ohio State University Extension (Ohioline) |
| Sheep intake | New Mexico State University Cooperative Extension (Circular 685); Oregon State University Extended Campus (ANS 312) |
| Alpaca & llama intake | Penn State Extension ("Copper Nutrition in Camelids"; "Feed Analysis: It's All About Energy"); Rutgers NJAES (FS917); UC Agriculture & Natural Resources |
| Donkey intake | Cornell Cooperative Extension (Ulster County); Merck Veterinary Manual; Smithsonian's National Zoo & Conservation Biology Institute |
| Feeding waste by method | N.C. Cooperative Extension; Penn State Extension; Nutrena / University of Minnesota |
| Storage loss by method | Mississippi State University Extension, "Hay Storage: Dry Matter Losses and Quality Changes"; University of Maryland Extension; N.C. Cooperative Extension |
| Hay storage sizing | Missouri Extension, "Sizing and Siting Hay Barns"; Extension Horses, "How much storage area is required for hay?"; University of Tennessee Extension, "Large Round Bale Hay Storage" (density sensitivity) |
| Winter livestock water | West Virginia University Extension, "Winter Watering for Livestock"; University of Nebraska–Lincoln CropWatch, "Pasture and Forage Minute: Winter Water Needs and Pasture Lease Considerations"; UC Agriculture and Natural Resources, "How Much Water Do My Animals Need Each Day?" |
| Horse & cattle manure | UMass Extension, "Manure Inventory" |
The current shipped calculator outputs do not depend on a numeric field still marked for verification. Storage outputs use the sourced per-ton planning rates instead of solid bale-volume geometry, so round-bale packing space is represented by the round storage rate rather than a cylinder assumption. No number changes without its source being logged in the same commit as the change, in this site's version-controlled data file. If you maintain BaleMath and want the line-by-line audit trail, it lives alongside the site's source code as data/DATA-SOURCES.md.
The judgment call
The defaults describe a mature, healthy animal at maintenance in ordinary weather, and real winters are not ordinary. In severe cold, North Dakota State University Extension reports cattle hay intake up to 3.5 percent of body weight; horse intake can likewise climb toward 3 percent. Pregnant and lactating animals need meaningfully more than maintenance figures allow, thin animals need more to regain condition, and poor hay means feeding more of it to deliver the same energy. The calculators expose weight, intake rate, and season length as inputs rather than hiding them, so adjust freely. The honest limit is this: someone who can see your animals and your hay — your hay grower, your vet, or the local extension office — beats any calculator, including these.
Everything on BaleMath is a planning estimate, built to get your tonnage, bale count, and budget close before you commit to a winter's supply. It is not veterinary or nutritional advice.