Tool
Horse rug calculator: temperature, wind and rain
This calculator is being revised. Its results use general rules that have not passed our source review. Do not use them as care advice for your horse.
What it does
- Works out the feels-like temperature: wind and wet take degrees off.
- Picks a step on the rug ladder, from no rug to 400 g of fill.
- Takes clipping, shelter and extra warmth (old, thin, unwell) into account, and says why.
What it doesn’t do
- Doesn’t know your horse: fat, thin, old or unwell changes the answer.
- Doesn’t replace feeling under the rug the next morning.
- Isn’t veterinary advice.
What happens to your input
What you enter stays in your browser and in the link, so you can share the result. Nothing is sent to a server; we only count that the tool was used.
How the rug guide calculates
First the feels-like temperature: from the temperature it subtracts what wind and wet take away in insulation (a moderate wind 2 °C, a strong wind 4 °C, a gale 6 °C; showers 1.5 °C, hours of rain 3 °C, and without shelter the wet counts one and a half times as much). Then the guide picks a step on the ladder for a healthy, unclipped horse with shelter: above 10 °C nothing, between 5 and 10 °C a rain sheet only when wet, a light fill around freezing, and one step heavier for every five degrees below that.
A partial clip adds one step, a full clip two, extra warmth needed one, and no shelter in frost one. Above a feels-like temperature of 15 °C, an unclipped horse that needs no extra warmth always gets “no rug”, even in rain.
That is deliberately one step lighter than most retailer charts: welfare charities say an unclipped horse usually needs no rug until around 5 °C, and horses that are allowed to choose leave the rug off in mild weather. In the US, read light, medium and heavy for 100, 200 and 300 g; switch the input to °F and the guide converts for you.
Questions
Which temperature do I enter?
The lowest temperature tonight at your yard, from the forecast. By day the rug can often be lighter or off.
My horse is overweight. Does that count?
Yes, in your favour: a horse in good to generous condition holds heat better. Don’t tick “Needs extra warmth”, and when in doubt choose the lighter rug.
Is the answer right for a pony?
Usually: a pony with a thick winter coat needs less, if anything. The exception is an old or thin pony.
In Halster
Keep a note of the blanket you chose
Note which blanket you chose yourself and the conditions when you checked it for your horse in Halster.
Install the test version through TestFlight.
Read next
Sources
- British Horse Society: Types of rugs and rugging a horse (reviewed 7 August 2026)
- World Horse Welfare: Rugging horses: when does your horse need a rug (updated 3 July 2026)
- Penn State Extension: When to blanket a horse