Horse hay calculator

How it works

Hay eaten per horse per day = body weight x the forage share (published range 1.5-2.5% of body weight, Alabama Extension, Decreasing Costs of Feeding Horses (2022), 2026-09-19). Put out per day = eaten / (1 - waste share), so what you put out covers what is trampled, soiled or blown away. Per week = per day x 7; per month = per day x 30.44 days (365.25 / 12). Bales = hay / bale weight, shown exact and rounded up to what you buy. The season figure = per day x the days in the months hay is fed, and it is also the year’s total, because hay is counted only for those months. Cost = bales (exact) x the price of a bale.

With the US starting values, hay for 5 months takes 96.4 (buy 97) bales; fed all year it takes 231.3 (buy 232). That is 4.4 (buy 5) bales a week, 177 lb of hay, and one bale lasts 2 days.

Every number is yours to change; the starting values only save typing. The forage share is a published planning figure for a horse at maintenance: a horse in work, a hard keeper or a cold winter push it up, grazing pulls it down, and bales vary a lot in weight, so weigh one. There are no live hay prices. All calculations run in your browser and the inputs stay there, so the Pro plan can pick up your horses.

Sources of the US starting values

• Body weight: Alabama Extension, Decreasing Costs of Feeding Horses (2022): worked example of a 500 kg horse, which needs 7.5 to 12.5 kg of dry matter a day — https://www.aces.edu/blog/topics/farming/decreasing-costs-of-feeding-horses/, read on 2026-09-19
• Forage, share of body weight: University of Maryland Extension, Calculating Your Horse's Winter Hay Needs (7 Apr 2021): horses should consume 2 % of their body weight in hay a day; Penn State Extension, Buying Winter Hay for Horses (27 Oct 2025): approximately 2-2.5 % — https://extension.umd.edu/resource/calculating-your-horses-winter-hay-needs and https://extension.psu.edu/buying-winter-hay-for-horses, read on 2026-09-19
• Forage range: Alabama Extension, Decreasing Costs of Feeding Horses (2022): leisure horses consume from 1.5 to 2.5 % of their body weight of forage on a dry-matter basis per day, never below 1.25 % — https://www.aces.edu/blog/topics/farming/decreasing-costs-of-feeding-horses/, read on 2026-09-19
• Hay waste: Penn State Extension, Buying Winter Hay for Horses (27 Oct 2025) and University of Maryland Extension, Calculating Your Horse's Winter Hay Needs (7 Apr 2021), small square bales: 13 % of the hay is wasted with no feeder (fed on the ground), 5 % in a hay rack, 3 % in a basket feeder, 1 % in a slat feeder; the no-feeder figure is the default (Penn State adds 5 % for storage) — https://extension.psu.edu/buying-winter-hay-for-horses and https://extension.umd.edu/resource/calculating-your-horses-winter-hay-needs, read on 2026-09-19
• Bale weight: Penn State Extension, Buying Winter Hay for Horses (27 Oct 2025) and University of Maryland Extension, Calculating Your Horse's Winter Hay Needs (7 Apr 2021): both assume a 40 lb small square bale = 18.14 kg — https://extension.psu.edu/buying-winter-hay-for-horses and https://extension.umd.edu/resource/calculating-your-horses-winter-hay-needs, read on 2026-09-19
• Bale price: No neutral source publishes a price per bale (it varies by region, cut and year); the bale weight comes from the page cited and the price is yours to type — https://extension.psu.edu/buying-winter-hay-for-horses, read on 2026-09-19
• Months hay is fed: Penn State Extension, Buying Winter Hay for Horses (27 Oct 2025): a 150-day winter, November through March = 5 months of hay (University of Maryland Extension, 2021, uses 1 December to 31 March = 121 days) — https://extension.psu.edu/buying-winter-hay-for-horses and https://extension.umd.edu/resource/calculating-your-horses-winter-hay-needs, read on 2026-09-19

UK and metric starting values have their own sources, shown under each field when you switch region.

Amounts are published averages for planning, not veterinary advice; a vet or an equine nutritionist decides what an individual horse needs, and any change to a ration should be made gradually.