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.com — corrections are genuinely welcome.
The method, in plain English
The cattle calculator is a hay-inventory planner, not a ration formulation tool. Its adjustable starting allowance is 2.5 percent of body weight as hay dry matter per day, following NDSU's winter inventory example. This is not a prediction for every cow: forage quality, production stage, other feeds and actual intake matter. Alternatively, enter the hay dry-matter allocation from an existing ration; the calculator does not subtract grain or balance nutrients.
Cattle method 2 separates dry matter, moisture and losses. Herd hay dry matter = animals × daily hay dry matter per animal × days. Divide by the hay dry-matter fraction to get hay actually eaten as-fed, then divide by (1 − feeding loss) and by (1 − storage loss). The 88 percent dry-matter starting value is an estimate, not a laboratory result; mark a measured value only when you have one. The method assumes a consistent hay dry-matter fraction across these planning stages.
The horse, goat, mixed-herd and round-versus-square planners now also use explicit hay dry matter and retained loss fractions. Enter an appropriate hay allocation or an explicit hay-DM percentage of body weight; no grain subtraction or cold-weather multiplier is applied. Intake and loss tables below are source references, not automatic defaults for these planners. Each round-versus-square option can have a different hay dry matter. Divide incoming purchase weight by measured bale weight and round once to whole bales. Nutritional adequacy and qualified review remain separate from arithmetic testing.
The other tools keep the same visible-input approach. The price converter normalises each offer to price per pound and per ton; when a visitor supplies lab-reported dry matter, it also removes water weight and compares price per pound or ton of dry feed. 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 source-specific daily output rates by animal weight and head count, then applies collection days and visitor-entered bedding.
The catch: the hay you buy is not the hay they eat
Every hay planner requires feeding and storage losses for the intended hay lot and period. Feeding loss is a fraction of offered hay; storage loss is a fraction of incoming hay. Work backwards by dividing by each retained fraction. Mississippi State Extension explains why storage conditions, moisture and duration matter. Cattle trials from Missouri Extension remain optional, explicitly identified examples on the cattle planner. Historical tables and worked examples retain their original source context; they are not automatic defaults for the other planners. A midpoint between unlike feeder observations is not a validated feeding-loss estimate.
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 offer, delivery, and optional forage-test 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.
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
Hay allocation depends on species, animal class, production stage, work, forage quality, other feeds and weather. A body-weight percentage must describe the hay portion on a dry-matter basis, not total diet intake. These tools do not balance energy, protein or minerals and do not automatically subtract grain. Use an appropriate existing ration or obtain qualified advice for the animals and hay involved. Arithmetic verification does not replace independent nutrition review.
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.