HorseCalcs: Bootstrapped Figures for the Working Rider
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Horse feed calculator

Most feed calculators come from feed companies. This one doesn't sell anything: it checks your horse's hay against the National Research Council's energy and protein requirements for its workload, and tells you how much concentrate, if any, closes the gap.

Enter your numbers
Your horse
Hay
Grass hay 0.8–0.95; alfalfa ~1.0
From your hay test; grass 8–12%, alfalfa 16–20%
Concentrate
Most grain mixes 1.3–1.6

Concentrate needed

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Energy needed
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Energy from hay
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Protein needed
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Protein supplied
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Hay as % of body weight
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Test your hay

Hay energy and protein vary widely, even within one field. A forage test costs about $25–40 through your extension office and replaces the estimates here with real numbers.

Where the requirements come from

The National Research Council's Nutrient Requirements of Horses (2007) sets daily needs by body weight and workload. For an average mature horse:

Digestible energy (Mcal/day) = body weight (kg) × 0.0333 at maintenance
× 0.0400 light · 0.0466 moderate · 0.0533 heavy · 0.0632 very heavy work
Crude protein (g/day) = body weight (kg) × 1.26 at maintenance, up to 2.01 for very heavy work

A 500 kg (1,100 lb) horse at maintenance needs about 16.7 Mcal and 630 g of protein a day. Good grass hay at 2% of body weight supplies about 20 Mcal, which is why many horses at light work don't need grain at all.

Hay first, grain second

Horses evolved to eat forage almost continuously. Feeding at least 1.5% of body weight as hay protects against colic and ulcers, and grain should only fill the energy that hay can't. When grain gets above about 0.5% of body weight a day, split it into several small meals.

Start with the horse weight calculator and the horse hay calculator. This calculator covers energy and protein only; talk to your vet or an equine nutritionist about minerals and special diets.

Frequently asked questions

Why does workload change the energy number so much?

Energy needs scale up substantially with exercise intensity — the NRC's own multipliers roughly double from maintenance to heavy work — because muscle activity burns considerably more calories than simply standing in a pasture.

What if hay alone already covers my horse's needs?

That's a common and good outcome — if the calculator shows hay meeting or exceeding the energy and protein targets for that horse's workload, no concentrate (grain or commercial feed) is needed on top of it, and adding more could contribute to excess weight.

Why doesn't this calculator sell a specific feed product?

It's built around the National Research Council's published nutrient requirements rather than any one brand's formulation, so the concentrate gap it shows is a nutritional target you can fill with whatever feed you choose, not a pitch for a particular product.

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