Horse Rug Fill Weight Guide: 150g, 220g, 250g & 300g for Australian Conditions

Choosing the Right Polyfill Weight for Your Horse: An Australian Guide

Updated March 2026

A practical, no-nonsense guide for Australian horse owners on understanding polyfill weights, how they work, and which fill is right for your horse, your climate, and your state.

Walk into any feed store or browse any equestrian website and you'll find winter rugs advertised with fill weights of 150g, 220g, 250g, 300g and beyond. But what does that actually mean for your horse? And more importantly - which one do you need? This guide cuts through the confusion so you can make the right call without having to ask.

What is polyfill and how does it work?

Polyfill is a synthetic insulation fibre - similar to what you find inside a pillow or a puffer jacket. In a horse rug, it comes in flat rolled sheets stitched between the outer shell and lining. The number you see on a rug (e.g. 300g) refers to how much polyfill is used per square metre of that sheet - not the weight of the whole rug.

Polyfill works by trapping air in thousands of tiny pockets within the fibre. Those air pockets slow the escape of heat radiating from your horse's body. The more polyfill per square metre, the more air pockets, and the warmer the rug. Think of it exactly like a doona on your bed - a 300g quilt is noticeably warmer than a 150g one for exactly this reason. The outer shell handles waterproofing and durability independently of the fill - for more, see our Horse Rug Waterproofing Guide.

Not all polyfill is equal. Better-quality polyfill uses a more open weave structure that bounces back over time rather than compressing and losing loft. A cheaper fill may be rated at 300g but perform closer to a good-quality 200g fill after a season of use. At Delzani, we use premium polyfill selected for long-term loft retention - the warmth you buy on day one is the warmth you get in year two.

Understanding the fill weights at a glance

Here's where each fill weight sits and who it's best suited for:

The Delzani winter rug range

All four rugs in the Delzani winter range are neck combos - full coverage from the moment you rug up. Here's how they compare:

Browse the full Delzani winter rug range →

Why 150g exists - and when it actually makes sense

A 150g fill is genuinely useful, but it's often misunderstood. It is not a winter rug for most of Australia - it's a shoulder season rug, a mild night layer, or a base layer worn under a heavier fill. Think of it as the equivalent of a light fleece jumper: fine on a cool autumn evening, not enough when the temperature drops hard. The 150g is ideal for Queensland winters, coastal New South Wales during early May or late August, and for horses that simply feel the cool but don't need serious insulation. It's also the right call for a clipped horse needing just a light top layer on a mild night.

The 220g - Australia's most underrated fill weight

The 220g is the fill that most horse owners overlook, jumping straight from 150g to 300g. That's a mistake. In much of southern Queensland, coastal New South Wales, and Perth, a 220g is the right mid-season workhorse - warm enough for cool nights but not so heavy that you're roasting your horse on a sunny winter afternoon. It also allows you to rug earlier in the season without the over-rugging risk that comes with a heavier fill. For Thoroughbreds, Standardbreds, and other fine-coated breeds in moderate climates, the 220g often hits the sweet spot.

The 250g - the quiet achiever

If you want one rug that handles the bulk of the Australian winter without needing an under rug underneath, the 250g is often your answer. It covers cold nights in Victoria, inland New South Wales, elevated South Australia, and the cooler parts of Western Australia without crossing into overkill territory. For healthy horses in good condition, the 250g typically handles nights down to around 2°C-4°C without an under rug. It's also the most versatile option for horses that move between climates - travelling from Sydney to the Snowy Mountains for competition, for example.

The 300g - not just for the south

The 300g is the standard for Tasmania, alpine Victoria, the ACT, and any property that regularly sees nights below 0°C. But it's also the right choice for specific horses anywhere in Australia - including Queensland. Older horses, horses that have lost condition, Thoroughbreds and Warmbloods with fine coats, and any horse that visibly shivers or loses weight in winter can all benefit from a 300g regardless of postcode. Many QLD owners simply prefer the confidence of a 300g, knowing their horse is well covered no matter what the night brings. When in doubt between 250g and 300g for a sensitive or older horse, anywhere in the country - choose 300g.

Your paddock matters as much as your postcode

The temperature on your phone's weather app is recorded at a Bureau of Meteorology station - often kilometres from your property, at a standardised height, in open conditions. What your horse actually experiences overnight can be quite different. Two properties in the same town can have meaningfully different effective temperatures depending on their environment. Here's what actually matters:

Wind: This is the biggest single variable after temperature itself. A still night at 5°C is very manageable for most horses. A 5°C night with a strong southerly blowing across an exposed paddock is a different situation entirely. Wind strips heat from a horse's coat the same way it chills you walking to the car without a jacket. If your paddock is exposed to prevailing winds with no natural break, add one fill weight to whatever the temperature alone suggests.

Rain and wet conditions: A horse's coat is a remarkably effective insulator when dry - the individual hairs trap warm air close to the skin. Once that coat is wet, that insulation collapses almost entirely. A wet horse in a 10°C night is losing body heat at a rate that a dry horse at the same temperature is not. This is why a rain sheet earns its place even on mild wet nights, and why a wet rug is worse than no rug at all - always check that your waterproofing is holding.

Dew and overnight moisture: Even without rain, heavy overnight dew in humid areas - articularly near creeks, dams, rivers or low-lying ground — can saturate a horse's coat by morning. Don't underestimate dew. It's one of the most common causes of a horse being colder than the temperature forecast would suggest.

Elevation: Temperature drops roughly 1°C for every 100 metres of elevation gain. If you're on a property at 800 metres above sea level, your effective overnight temperature is consistently around 8°C colder than the nearest coastal town. This is why places like Armidale, Stanthorpe, the Southern Tablelands, and the Victorian high country get so much colder than their latitude alone would suggest - and why horses in these areas consistently need one fill weight more than owners initially expect.

Cold air pooling: Cold air is denser than warm air and flows downhill overnight, pooling in low-lying areas, gullies, creek flats and valley floors. If your horse sleeps in a low paddock near a creek, it may be sitting in air that is 3°C to 5°C colder than the paddock on the rise above it - even on the same property. This is worth knowing if you have horses in different paddocks and are trying to apply one rugging rule across the lot.

Shelter and natural windbreaks: A good stand of trees, a well-positioned shed, or even a dense hedge makes a measurable difference to what a horse experiences overnight. A horse with access to effective shelter can often manage one fill weight lighter than a horse in an open, exposed paddock at the same temperature. Conversely, if your shelter is poorly positioned - facing the prevailing wind, too small, or too far from where the horse actually stands at night - it offers little practical protection.

Ground conditions: Wet, boggy paddocks are colder environments than dry ones. Mud conducts heat away from hooves and legs and increases the general dampness of the horse's environment overnight. Horses standing in wet ground for hours lose body heat through their feet more readily than horses on dry ground.

Hay and feed: Worth mentioning because it is genuinely relevant to rugging decisions. Digestion of fibre in a horse's hindgut generates significant internal heat - a horse with good access to quality hay overnight is better equipped to stay warm than one on poor pasture or restricted feed. If your horse is on limited feed through winter, compensate with a heavier rug. The two work together.

The daytime-to-overnight swing: Australian winters are famous for warm days and cold nights, particularly inland. A rug appropriate for a 3°C overnight low may be completely wrong by 1pm the following day if temperatures climb to 18°C. This is the most common cause of over-rugging in Australia - the rug goes on at night and nobody takes it off in the morning. Build a habit of checking and adjusting at the same time each day, and if you can't check mid-morning, the Dakota's detachable neck gives you one easy way to reduce coverage without a full rug change.

State-by-state guide: which fill for where you live *

* State recommendations are a general starting point based on typical regional climate patterns. Your property, your paddock, and your horse are unique. A horse in a sheltered valley will experience winter very differently to one on an exposed hilltop in the same postcode. Always use these guidelines alongside your own daily observations - no guide knows your horse better than you do.

Your horse's individual needs matter as much as the temperature

The guides above assume a healthy adult horse in moderate condition with a natural winter coat. The following factors should push you toward a heavier fill regardless of where you live:

Breed and coat type: Thoroughbreds, Standardbreds, and Warmbloods have finer coats and feel the cold more. Go up one fill weight from what the climate alone suggests.

Age: Young horses (under 3) and older horses (15+) are less efficient at regulating body temperature. Go up one weight during winter, especially if nights are cold.

Condition: A horse in good condition has natural insulation. A thin horse in poor condition loses heat quickly - a heavier fill is essential.

Clipping: A full clip in mid-winter requires a 300g as a minimum. A trace clip still removes enough coat to push you up one fill weight.

Stabled vs turned out: Wind chill significantly increases the effective cold felt by a turned-out horse. In wet, windy conditions - rug heavier and check regularly for signs of overheating.

A few more things worth knowing

Horses in work vs spelling: A horse in regular work generates significantly more body heat than one standing in a paddock all winter. A fit, actively worked horse in Ballarat may genuinely be comfortable in a 250g where a horse spelling in the same paddock needs a 300g. Factor in workload - it's not just about the temperature outside.

Water access: Horses drink less when water is very cold, and a dehydrated horse thermoregulates poorly. In cold snaps, check troughs daily - not just for ice, but for temperature. A horse reluctant to drink cold water overnight is burning more energy staying warm and may need more feed and a slightly heavier rug to compensate. This is particularly relevant on properties with exposed metal troughs in alpine and tablelands areas where overnight temperatures drop hard and fast.

Horses in work - rugging after exercise: Never rug a hot horse immediately after work. Rugging before your horse has properly cooled down traps sweat and heat under the rug, which can cause skin issues, overheating, and rug rub. Walk your horse out, let the coat dry, and then rug. In cold conditions a wool or fleece cooler worn loosely while walking out is the right tool - it wicks moisture while allowing the horse to cool gradually before the winter rug goes on.

Mud fever and rain scald: Wet winters create ideal conditions for mud fever on legs and rain scald across the back and rump. A well-fitted waterproof rug dramatically reduces rain scald risk by keeping the coat dry. However, a poorly fitting rug that lets water in, or one with failing waterproofing, can actually make conditions worse by trapping moisture against the skin. Check the fit and the waterproofing regularly - particularly after heavy rain. If you're seeing rub marks or damp patches under the rug, address it immediately.

Rugging young horses: Foals and yearlings have a much higher lower critical temperature than adult horses - they feel the cold at temperatures that a mature horse handles comfortably. A foal in its first winter in alpine or elevated areas should be rugged earlier in the season and checked more frequently than the adults in the same paddock. Growing horses also burn more energy through winter, so feed and rug go hand in hand.

The acclimation window: Australian winters don't arrive overnight. Horses acclimatise gradually as temperatures drop through autumn - their coat thickens, their metabolism adjusts, and their lower critical temperature shifts accordingly. This means a 10°C night in late May is felt very differently to a 10°C night in late July by the same horse. Rug up gradually as the season changes rather than waiting for the first cold snap and reaching for the heaviest option straight away.

The layering approach: more flexible than a single heavy rug

A base layer (150g-220g) worn under a mid-weight rug gives you flexibility as temperatures fluctuate through the season. Remove the under rug on warmer days, add it back as temperatures drop - without needing to buy multiple full rugs. This approach also extends the life of each individual rug since no single one is worn every day.

Signs your rug choice is wrong

Too cold: shivering, tense muscles along the topline, reluctance to move, hunched posture, weight loss.

Too warm: sweating under the rug (particularly at the neck and shoulders), damp lining, restlessness, loss of appetite.

Over-rugging is just as problematic as under-rugging. A horse that cannot cool down properly is at risk of heat stress and skin issues from trapped sweat.

Delzani rugging temperature guide

Use this as your starting point. All recommendations assume a healthy adult horse with a natural winter coat. Adjust up one fill weight for clipped, fine-bred, older, young, or thin horses.

Frequently asked questions

Putting it together: a simple decision guide

If you are in QLD or coastal areas, start with 150g-220g. If you are in VIC, ACT, TAS, or elevated inland areas, start with 300g. Everywhere else - NSW inland, SA, WA hills - 220g-250g is your range. Then adjust up one weight if your horse is old, young, thin, clipped, fine-bred, or turned out in wet and windy conditions. Adjust down one weight if your horse is a hardy native breed in good condition with a full natural coat and access to good shelter.

Explore the Delzani Winter Rug Range · All Horse Rugs · Rug Accessories & Liners · 600D vs 1200D - Understanding Denier · Horse Rug Waterproofing Guide.

Written by Jane Griffiths - An experienced Australian horse owner and product developer with over three decades immersed in equestrian life. Jane has spent years refining horse rugs, tack, and riding apparel to better suit Australian climates. She has enjoyed countless weekends at gymkhanas, show jumping events, and pony club competitions with her daughter, and still loves hitting the trails with friends whenever she can. Her lifelong passion for horses and hands-on understanding of equine comfort continue to shape her practical, rider-first approach to horse care and product design.