Why use this calculator
Knowing your yield three weeks before the header starts changes what you can do about it. Storage has to be cleaned and sized, chaser bins and trucks have to be booked, contract tonnage has to be committed or left open, and cash flow has to be planned against a number rather than a hope.
Paddock counts are the only way to get that number, and the arithmetic behind them is easy to get wrong by an order of magnitude if row spacing is mishandled. This tool does the conversion properly, in both metric and imperial, and then does the two things most yield calculators skip: it takes off realistic harvest losses, and it converts your harvest moisture into the tonnes the receival site will actually pay you for.
How to use it
- Pick the crop, which sets the standard receival moisture and the bushel weight used for imperial conversion.
- Enter the row spacing as sown, since that is what turns heads per metre of row into heads per square metre.
- Enter the length of a single row you counted along, usually one or two metres, and the number of fertile heads you counted in it.
- Thresh out at least ten representative heads and enter the average filled grains per head.
- Count and weigh two hundred grains to get thousand grain weight, then enter it in grams.
- Put in the moisture reading from the header or a hand meter, and the test weight from a chondrometer if you have one.
- Enter an expected harvest loss, the paddock area the sample represents, and the net grain price at the receival point.
What each result means
- Heads per square metre
- Fertile heads in a square metre, the density figure agronomists use to judge whether a crop established properly.
- Grains per square metre
- Heads per square metre multiplied by grains per head. Together with grain size this is the entire yield.
- Standing crop yield
- Tonnes per hectare sitting in the paddock before the header takes anything off, at harvest moisture.
- Yield after harvest losses
- What actually reaches the bin once shattering, header loss and handling are taken off the standing crop.
- Grain value lost at the header
- The dollar value of the grain your harvest loss percentage leaves on the ground, per hectare and for the whole paddock, at the price you entered.
- Yield paid at receival
- Tonnes per hectare after moisture shrinkage, which is what the weighbridge ticket and your payment will be based on.
- Moisture adjustment
- How much weight moisture costs you, either shrunk back at delivery or given away by harvesting drier than the standard.
- Yield per acre
- The same paid yield expressed in tonnes per acre, for comparing with imperial benchmarks or older records.
- Bushels per acre
- Paid yield converted using the crop's bushel weight, the standard unit in North American markets.
- Test weight
- Hectolitre weight, a grade determining measure of grain plumpness. Low test weight downgrades an otherwise sound crop.
- Total paddock production
- Paid tonnes across the whole paddock, the number to size storage, trucks and contracts against.
- Gross value per hectare
- Paid yield multiplied by your net price, before growing costs. Compare it against cost per hectare to see the margin.
- Gross value of the paddock
- Whole paddock revenue at the price you entered, which is the cash flow figure to plan against.
The formula
Heads per square metre equals heads counted divided by the sampled row length in metres, divided by the row spacing in metres. Yield in tonnes per hectare equals heads per square metre multiplied by grains per head multiplied by thousand grain weight in grams, divided by 100,000. Yield after losses equals that multiplied by one minus the loss percentage. Paid yield applies moisture shrinkage, multiplying by (100 minus harvest moisture) divided by (100 minus the standard receival moisture) whenever harvest moisture is above standard. Standard receival moisture is 12.5 per cent for wheat, barley and oats, 13.5 for sorghum, 14 for maize, 13 for soybeans and 8 for canola. Bushels per acre equals tonnes per hectare multiplied by 892.179 divided by the bushel weight in pounds.
How this number is used in practice
Sampling discipline decides whether the estimate is worth anything. A single count beside the gate will flatter almost any paddock, because headlands, the good flat near the shed and the sandy rise are all different crops. Take at least eight to ten counts on a diagonal transect, drop the highest and lowest if one is clearly atypical, and average the rest.
Where a paddock has genuinely distinct zones, count and run each zone separately and weight the answer by area. Counts taken after flowering but before grain fill finishes will need a thousand grain weight estimate rather than a measurement, which is the largest single source of error in an early estimate.
Moisture is a cost most growers only feel at the weighbridge. Delivering wheat at 14 per cent against a 12.5 per cent standard shrinks the paid weight by roughly 1.7 per cent, which on a thousand tonne delivery is seventeen tonnes of grain you grew and will not be paid for, plus a possible drying charge.
Delivering at 10.5 per cent is not free either: you were entitled to sell water up to the standard and you did not, which on the same delivery is about twenty three tonnes of foregone weight. Harvesting close to but not above the standard, and using aeration to bring slightly damp grain down rather than leaving it in the paddock, is where the money is.
Test weight is the quiet grade risk. A crop can look excellent, yield well and still be downgraded because a hot finish or a late frost left the grain pinched. Most Australian milling wheat grades require at least 74 kilograms per hectolitre, and falling below it can move a load from a milling grade to feed, with a price difference far larger than anything in the yield estimate.
Check test weight on a sample before you commit a load to a particular grade, not after the truck has tipped.
Worked examples
Wheat: 120 heads over 2 m of row at 25 cm spacing, 28 grains, 34 g TGW, 13.5 per cent moisture, 120 ha
About 2.28 t/ha standing and roughly 2.15 t/ha paid at receival.
The same crop harvested dry at 10.5 per cent instead of 13.5
Paid yield is the bin weight of about 2.17 t/ha, with tonnes forgone against the standard.
Barley: 150 heads over 2 m at 30 cm spacing, 22 grains, 44 g TGW, 80 ha
About 2.42 t/ha standing yield.
When people use it
- Sizing storage, chaser bins and truck bookings before the header rolls
- Deciding how much grain to commit to a forward contract and how much to leave open
- Comparing paddock or zone performance to inform next season's inputs
- Assessing a crop after frost, hail or a hot finish to support an insurance claim
- Modelling what harvesting a point or two wetter or drier does to paid tonnes
- Converting an Australian yield to bushels per acre for a North American benchmark
Tips
- Take eight to ten counts on a diagonal across the paddock, not one beside the gate, and average them.
- Measure thousand grain weight rather than guessing it. It is the largest single source of error in an early estimate.
- Count only fertile heads. Late tillers that will not fill inflate the estimate badly in a dry finish.
- Sample zones separately where a paddock has distinct soil types, then weight the result by area.
- Knock five to ten per cent off for harvest losses. A well set header still leaves grain behind.
- Check test weight on a sample before committing a load to a milling grade, because the price gap to feed is large.
- Aim to harvest just under the receival standard. Delivering very dry gives away weight you were entitled to sell.
What it assumes, and where it stops being accurate
- Counts are assumed to represent the whole paddock. A biased sample produces a confidently wrong answer.
- Grain fill is assumed to complete normally. Frost, heat or moisture stress after sampling will cut thousand grain weight.
- Screenings, foreign material and unfilled grain are not deducted separately beyond the harvest loss percentage.
- Receival moisture standards are the Australian trading standards and differ overseas, notably for maize and soybeans in the United States.
- Bushel conversions use standard bushel weights, which are trading conventions rather than measured densities of your grain.
- Price is a flat net figure. Grade spreads, protein payments, drying charges and storage costs are not modelled.
Terms used on this page
- Thousand grain weight
- The weight in grams of 1,000 grains, the standard measure of grain size.
- Receival moisture
- The moisture percentage a delivery is adjusted back to for payment, 12.5 per cent for Australian wheat.
- Test weight
- Grain weight per hectolitre, a grade determining measure of plumpness and packing density.
- Shrinkage
- The reduction in paid weight applied when grain is delivered above the standard moisture.
- Bushel
- An imperial volume measure converted to weight by a crop specific standard, 60 pounds for wheat.
Questions people ask
- How do I estimate grain yield before harvest?
- Count fertile heads along a measured length of one row, thresh ten heads to get average grains per head, and weigh 200 grains to get thousand grain weight. Convert heads per metre of row to heads per square metre using row spacing, then multiply heads by grains by thousand grain weight and divide by 100,000 for tonnes per hectare.
- How do I measure thousand grain weight?
- Count out exactly 200 grains, weigh them on accurate scales and multiply by five. Two hundred grains weighing 6.8 grams gives a thousand grain weight of 34 grams. Typical ranges are wheat 30 to 45 grams, barley 38 to 50, oats 25 to 40 and canola 3 to 5, so a figure far outside those suggests a counting error.
- What is moisture shrinkage and what does it cost?
- Receival sites pay on weight adjusted to a standard moisture, which is 12.5 per cent for Australian wheat. Delivering at 14 per cent shrinks paid weight by about 1.7 per cent, so a thousand tonne delivery loses roughly seventeen tonnes plus any drying charge. Delivering below standard earns no bonus, so very dry grain gives away saleable weight.
- Why does test weight matter if my yield is good?
- Because test weight determines grade, and grade determines price. Most Australian milling wheat grades require at least 74 kilograms per hectolitre. A pinched sample from a hot finish or a late frost can yield acceptably and still be downgraded to feed, and the price gap is usually far larger than any difference in tonnes.
- How do I convert tonnes per hectare to bushels per acre?
- Multiply tonnes per hectare by 892.179 and divide by the crop's bushel weight in pounds. Wheat and soybeans at 60 pounds give 14.87 bushels per acre for each tonne per hectare, barley at 48 pounds gives 18.59, maize and sorghum at 56 pounds give 15.93, and oats at 32 pounds give 27.88.
- How many samples should I take across a paddock?
- At least eight to ten, spread on a diagonal transect that crosses the different soil types rather than following a single contour. Avoid headlands and gateways, which are never representative. Where the paddock has genuinely distinct zones, sample and calculate each zone separately, then weight the results by the area of each zone.
Use this with
Harvest Yield Estimator answers one part of the question. These pick up where it stops: Crop Yield Estimator, Seed Rate Calculator, Cost Per Hectare Calculator, Crop Rotation Nitrogen Credit Calculator and Soil pH and Lime Rate Calculator.
Where these figures come from
Figures and rules on this page follow Australian law and ATO guidance.
- Grains Research and Development Corporation. Australian grains agronomy, nitrogen budgeting and yield estimation research
- Grain Trade Australia. Commodity trading standards, including receival moisture and test weight limits
- United States Department of Agriculture. US grain standards, bushel weights and livestock production statistics
- ABARES, Australian Bureau of Agricultural and Resource Economics and Sciences. National farm performance, commodity price and production data
Harvest Yield Estimator produces an estimate for general information. It is not financial, tax, medical, legal or engineering advice. read the full disclaimer. Spotted a wrong number? Report it and it gets fixed. The form picks up this calculator and the inputs you used.