Horse Blanket Calculator (Sheet, Light, Medium or Heavy by Temperature, Clip, Wind, Rain & Age)
Decide whether and how heavily to blanket a horse tonight from the temperature, wind chill and rain, its coat and clipping, shelter, body condition and age, with the fill weight in grams, when to change or remove it, and the signs of an over- or under-blanketed horse.
How it works
felt temperature = low + wind (−5 breezy, −12 windy) + rain (−12) or snow (−4), scaled by shelter (stall ×0.2 wind, 0 rain, +10 °F; run-in ×0.5, +4 °F) · comfort limit: full coat 18 °F, trace clip 28, hunter clip 38, body clip 48, summer coat 41; +10 thin/senior/foal, −5 overweight, +8 unacclimatised · margin = felt − limit: ≥ 0 none/sheet; to −10 light; to −22 medium; to −35 heavy; below heavy + liner
Horses are built for cold: a full winter coat, a big hay-digesting gut and a wind break keep a healthy horse comfortable well below freezing, and blanketing one that does not need it does harm — it flattens the coat, traps sweat and hides weight loss. The decision changes when the coat is clipped for work, when rain and wind strip its insulation, and for thin, old, young or newly arrived horses. This calculator estimates the temperature the horse actually feels, compares it with the comfort limit for its coat and condition, and turns the gap into a blanket weight.
Worked example
A healthy, acclimatised horse with a full coat, out with a run-in shed on a breezy, dry 35 °F night: the shed offsets most of the wind, so it feels like about 37 °F against an 18 °F comfort limit — no blanket. The same night with a hunter clip (limit 38 °F) calls for a light 100 g turnout; add rain with no shelter and the felt temperature drops to about 18 °F, so the clipped horse needs a medium 200 g waterproof.
Frequently asked questions
At what temperature does a horse need a blanket?
A healthy adult with a full winter coat, shelter and plenty of hay generally does not until around 10–20 °F, or about 30–40 °F in cold rain and wind. Clipped horses need one from roughly 40–60 °F depending on the clip; seniors, thin horses and those moved from a warm climate blanket earlier.
What do the gram weights mean?
Grams of polyester fill per square metre: 0 g is a sheet (wind and rain only), 100 g light, 200–250 g medium, 300–400 g heavy. A liner (100–200 g) under a medium gives a heavy without buying one; a neck cover adds warmth for clipped horses.
Is it bad to blanket a horse that does not need it?
Yes: the blanket stops the coat from standing up (its main insulation), so the horse is often colder than naked if the blanket is too light, and overheats and sweats if it is too heavy — then chills when the sweat cools. It also hides weight loss and rubs. When in doubt, shelter and hay first.
Related calculators
Equine figures are planning estimates from common husbandry references (NRC 2007, extension services). Individual horses, forage quality, climate and workload vary — weigh hay, body-condition score regularly and work with your vet, farrier and nutritionist.