A grain auger is one of those tools you never think twice about until harvest is on and the one sitting in the yard turns out to be too short to reach the bin or too slow to keep up with the combine. Getting the size right the first time saves you money, saves you time, and saves a lot of standing around waiting on grain to move. Whether you are augering out of a hopper, filling a tall bin, or loading a truck, the auger has to match three things at once: your bin, your grain, and your power source.
This guide walks through the numbers that actually matter — length to reach your fill point, diameter for the bushels per hour you need, and the horsepower to drive it — plus the swing-away versus conventional question that trips up a lot of buyers. Once you know your numbers, farmpages.com/ makes it easy to find and compare suppliers who carry the right unit for your operation.
Quick answer: Size a grain auger by length, diameter and power. The length must reach the peak of your tallest bin at a 30 to 45 degree working angle, with reach to spare. Diameter sets capacity, so match or beat your combine’s unload rate: an 8 or 10 inch auger suits most single-combine farms, while larger operations move to 13 or 16 inch swing-aways. Then confirm PTO horsepower or yard electrical service.
1 Start With the Job, Not the Price Tag
Before you look at a single price, be honest about the job the auger has to do. A 30 foot utility auger that empties a hopper bin is a very different animal from a swing-away that has to feed a 20,000 bushel bin during a hard-run harvest. Ask yourself how fast your combine unloads, how tall your bins are, how far the auger has to travel across the yard, and whether you are moving wheat, canola, barley, corn or peas.
Grain type alone changes rated capacity, because light seed like canola flows differently than heavy corn. Buying to the busiest day of your year, not the average day, is almost always the right call.
2 Grain Auger Sizes: Getting the Length Right
Length is the first spec people get wrong, usually by going too short. The auger has to reach the bin’s fill point while sitting at a sensible working angle — most augers are rated for good flow somewhere around 30 to 45 degrees, and standing one up steeper than that both cuts capacity and strains the driveline. That means the raw length you need is more than just the height of the bin.
Grain auger sizes are commonly listed by length and diameter together, for example a 10 inch by 60 foot swing-away. To figure out the length, work through the reach math for your tallest bin.
- Measure the bin’s eave (sidewall) height and the peak height where the fill spout actually sits.
- Add the height of the truck box or hopper you need to clear at the intake end.
- Account for the operating angle — the steeper the auger, the shorter its reach for a given length.
- Leave yourself reach to spare so you are not maxed out on every single bin.
- Check where the intake sits when the auger is set at working angle, not lying flat on the ground.
- Confirm the auger clears bin ladders, rings and roof fittings on the way up.
Tip: if you are planning to add taller bins down the road, buy a few feet longer than today’s yard needs. Length is cheap to buy once and expensive to wish for later.
3 How Diameter Drives Capacity
Diameter is what sets your capacity. A bigger tube moves more grain per turn, so as you step up in inches you step up in bushels per hour — but you also need more horsepower to turn it. The figures below are typical ranges as of 2026 and will vary with grain type, auger speed, pitch and flighting, so treat them as a planning guide rather than a guarantee. Use this auger capacity chart to line diameter up against the throughput you actually need.
| Diameter | Typical capacity (bu/hr)* | Common use |
|---|---|---|
| 6″–7″ | ~1,500–3,500 | Utility work, augering out bins, small yards |
| 8″ | ~3,500–6,000 | All-round farm auger, bin transfer |
| 10″ | ~6,000–9,000 | Keeping up with a single combine |
| 13″ | ~9,000–13,000 | High-capacity, multi-combine harvest |
| 16″ | ~13,000–18,000+ | Large commercial operations |
*Ranges are approximate and depend on grain type, auger speed, angle and spec.
As a rough rule, you want the auger to at least match your combine’s unload rate so you are never the bottleneck at the bin. Names you will see across Western Canada and the Upper Midwest include a range of established auger and conveyor makers:
Wheatheart Meridian Westfield Farm King Brandt Sakundiak Batco
Any of these can be lined up and compared through the FarmPages listings of grain-handling equipment suppliers in your area.
4 Horsepower and Drive: PTO vs Electric
Diameter decides how much grain the auger can move; horsepower decides whether it actually will. Undersize the power and the auger bogs, overheats, plugs and wears the gearbox out early. There are a couple of common ways to drive one, and the right choice usually comes down to whether you already have a tractor free at harvest.
PTO Drive
Runs off the tractor’s power take-off. Mobile, high capacity, and ideal for moving between bins and out to the field. The trade-off is that it ties up a tractor with enough PTO horsepower, and the spinning driveline must be guarded.
Electric Drive
Clean, quiet and set-and-forget for a fixed bin site — no tractor needed. The catch is that big augers need a serious electrical service, often three-phase or a large single-phase motor, so your yard power has to be up to it.
As a rough guide, horsepower climbs steadily with diameter and length: small utility augers may need only single digits to the low teens, mid-size 8 to 10 inch units run in the tens of horsepower, and big 13 inch swing-aways can call for a hundred PTO horsepower or more. Gas and hydraulic drives exist too, mostly on portable and specialty units.
Warning: never run an auger below its rated horsepower or with a slipping, worn PTO shaft. An underpowered or poorly guarded auger is both a breakdown and a safety hazard waiting to happen. Match the drive to the auger, keep guards in place, and shut it down before anyone goes near the intake.
5 Swing-Away vs Conventional
This is the decision that shapes the whole purchase. A swing away auger uses a low hopper on a swing arm so you can back a truck or trailer over the intake and drive away, which is why they dominate on high-capacity yards. A conventional auger has a fixed intake you shovel or hopper-feed into — simpler and cheaper, but slower to work with day to day.
Swing-Away Auger
Low, driveover hopper means no shovelling. High capacity, feeds big bins fast, keeps trucks moving. More moving parts, higher purchase price, and it needs room to swing and set up. Best for busy multi-combine harvests and larger bins.
Conventional Auger
Fixed intake, simpler build, lower cost, and quick to set up in tight spots. You feed it manually or with a hopper cone. Lower capacity and more labour. Best for smaller yards, transfer work and augering out.
6 Buying Smart: A Grain Auger for Sale Checklist
When you are looking at a grain auger for sale, weigh a few last things before you commit. Portability matters if you move between yards — check the transport width, wheel setup and how it hitches. Mover kits, hydraulic lift and reverse-flow features add convenience but also cost. And think about how the auger fits the rest of your grain system, right down to the building it lives beside.
- Match diameter to your combine’s unload rate so the auger is never the bottleneck.
- Size length to your tallest bin’s peak, plus working-angle reach and a margin.
- Confirm your power source — tractor PTO horsepower or yard electrical service — before you buy.
- Decide swing-away versus conventional based on how much grain you move on your busiest day.
- Check transport width, mover options and warranty on any used unit.
- Buy for the operation you will have in five years, not just today.
The auger is only one piece of the grain system, of course. If you are also planning storage and shelter around it, our look at a Quonset hut versus a pole barn covers the building side, and if you are budgeting equipment across the whole operation, our comparison of a disc harrow versus a field cultivator is worth a read too.
7 Grain Auger FAQ
What size grain auger do I need for my bins?
Size the length to reach the peak of your tallest bin at a 30 to 45 degree working angle, and size the diameter to match or beat your combine’s unload rate. For most single-combine farms an 8 or 10 inch auger in the right length handles day-to-day filling; larger operations move up to 13 or 16 inch swing-aways.
How is grain auger capacity measured?
Capacity is rated in bushels per hour, but that number assumes a specific grain, auger speed and operating angle. Light grain like canola and steep angles both reduce real-world capacity, so always read the rating against the grain and setup you actually run.
What horsepower does a grain auger need?
It climbs with diameter and length. Small utility augers may need only single digits to the low teens of horsepower, mid-size 8 to 10 inch units often need tens of horsepower, and big 13 inch swing-aways can call for a hundred PTO horsepower or more. Always match or exceed the manufacturer’s rating.
Is a swing-away auger worth the extra cost?
If you move a lot of grain, yes. The driveover hopper saves labour and keeps trucks moving during harvest. For a small yard that only augers out a few bins a year, a conventional auger is usually the more sensible buy.
Where can I find a grain auger for sale near me?
Use the FarmPages directory to browse and compare grain-handling suppliers near you, then contact them directly to check stock, spec and pricing.