A volume that is sold by weight
The bushel started as a container. It is a volume — exactly 2150.42 cubic inches, or 35.239 litres — and it is the same volume whether it holds wheat, oats or sunflower seed. What differs is what that volume weighs, and the grain trade settles on the weight.
So each commodity has a standard test weight: the pounds a bushel of it is taken to weigh. Those figures are fixed by convention and written into grade tables, and they are the reason a bushel has no single conversion to kilogrammes.
The same 35.24 litres, by crop| Crop | lb per bushel | kg per bushel | Bushels per tonne |
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| Wheat, soybeans | 60 | 27.22 | 36.74 |
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| Maize, sorghum, rye | 56 | 25.40 | 39.37 |
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| Canola | 50 | 22.68 | 44.09 |
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| Barley | 48 | 21.77 | 45.93 |
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| Rice (rough) | 45 | 20.41 | 48.99 |
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| Oats | 32 | 14.52 | 68.89 |
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| Sunflower seed | 28 | 12.70 | 78.74 |
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Top to bottom that is a factor of 2.14. A bushel of wheat is 1.875 times a bushel of oats — same volume, nearly twice the mass — because oats are light and hulled and simply do not pack as much into a container.
Which is why this converter asks for the crop and will not answer without it. A tool that quietly assumed wheat would be right for two of the eleven crops here and wrong by up to 114% for the rest.
Yield inherits the same problem
North American yields are quoted in bushels per acre and almost everywhere else in tonnes per hectare. The conversion between them contains the bushel weight, so it is a different factor for every crop.
Multiply bushels per acre by this to get tonnes per hectare| Crop | Factor | 100 bu/ac is |
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| Wheat, soybeans | 0.06725 | 6.73 t/ha |
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| Maize, sorghum | 0.06277 | 6.28 t/ha |
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| Canola | 0.05604 | 5.60 t/ha |
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| Barley | 0.05380 | 5.38 t/ha |
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| Oats | 0.03587 | 3.59 t/ha |
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| Sunflower seed | 0.03138 | 3.14 t/ha |
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Using the wheat factor on an oat crop nearly doubles the answer, and both numbers are in a range an oat crop could plausibly be. That is the failure mode: not an obviously silly result, just a wrong one.
The factor is worth understanding rather than memorising. It is the bushel weight in pounds, converted to tonnes and divided by the acre in hectares — so a crop with twice the bushel weight has twice the factor, and nothing else about the crop enters into it.
India and much of Europe quote yield in quintals per hectare, which is simply ten times the tonnes-per-hectare figure. That one is a genuine unit conversion with no crop in it at all, which makes it the easiest of the three to move between.
Two bushels and four hundreds
Two further ambiguities sit around the edges, both from words that were reused.
There are two bushels. The US dry bushel is 35.239 L and the imperial bushel is 36.369 — 3.2% larger. Modern grain trade uses the first, but older British and Commonwealth figures use the second, so a historical yield or a pre-metric record may be on the other one.
Four units that have all meant “a hundred”| Unit | Definition | Kilograms |
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| Quintal | 100 kg | 100.00 |
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| US hundredweight (short) | 100 lb | 45.36 |
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| Imperial hundredweight (long) | 112 lb | 50.80 |
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| Metric centner (historical) | 50 kg in some usages | 50.00 |
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A quintal is exactly 100 kg and is the working unit of Indian agriculture. The two hundredweights are 45.36 and 50.80 kg, both abbreviated cwt, and neither is a quintal. Reading an Indian price per quintal as a price per hundredweight overstates it by more than double.
The pattern is the same one that runs through the whole page: a word that meant “about this much” in one trade got fixed to a precise figure independently in several places, and the figures did not agree.
Moisture is part of the weight
A load of grain is partly water, and the buyer is not paying for water. So settlement is on the weight the load would have at the contract moisture, and the arithmetic is that dry matter is conserved.
100 tonnes delivered, settled at 15% moisture| Delivered at | Settles as | Difference |
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| 12% | 103.53 t | +3.53 |
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| 15% | 100.00 t | — |
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| 18% | 96.47 t | −3.53 |
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| 22% | 91.76 t | −8.24 |
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Three points of moisture on a hundred tonnes is three and a half tonnes of apparent weight, which is worth knowing before a load leaves rather than after the scale ticket arrives. Drying charges and grade discounts sit on top of this and vary by buyer.
Two cautions. Some contracts shrink on a different basis from the plain dry-matter calculation, adding an allowance for handling loss during drying — so the number here is the physics rather than necessarily the contract. And a load can be discounted for test weight as well as moisture: grain lighter than the standard bushel weight is graded down, which is a separate deduction from this one and uses the buyer’s own schedule.
Reading a figure from another country
Most of the confusion here is about which convention a number is already in. Three checks resolve nearly all of it.
A bushel figure needs a crop. If a source says “bushels” without naming what is in them, the tonnage cannot be worked out. Grain elevators, futures contracts and USDA reports all specify the commodity for exactly this reason.
A yield figure needs both a crop and a unit. “60” could be a strong wheat crop in bushels per acre, a very strong one in quintals per hectare, or an impossible one in tonnes. The three conventions differ by roughly a factor of ten each way, which at least makes a mistake obvious.
Metric figures are usually the safer common ground. Tonnes and hectares carry no crop-specific assumption, and quintals are exactly a tenth of a tonne. When comparing across borders, converting everything to tonnes per hectare first removes the crop from the problem entirely — and it is the unit international statistics are published in.
What none of this settles is price. Grain is priced per bushel in North America and per tonne or quintal elsewhere, and the conversion between those prices carries the same crop-specific weight — so a price per bushel and a price per quintal are not comparable without the same step.
Sources and methodology
The bushel test weights are the USDA figures that grade tables and yield conversions are written against. Everything else on this page is exact rather than measured: the pound, the acre and the US dry bushel have all been defined since 1959, and the quintal is exactly 100 kg — so every factor here follows from definitions with no experimental uncertainty in it.