Corn Bushel Per Acre Calculator

This calculator works out corn yield in bushels per acre from the number of harvestable ears, kernel rows per ear, and kernels per row. Enter those three field counts and you get an estimated yield at 15.5% moisture, the standard for No. 2 yellow corn. The result is a planning estimate, not a substitute for a scale ticket, but it is the same method agronomists use for pre-harvest checks.

Formula

The standard yield component formula is:

Yield (bu/acre) = (ears per 1/1000 acre × rows per ear × kernels per row) ÷ 90

Where:

• Ears per 1/1000 acre – count of harvestable ears in a length of row equal to 1/1000 acre (see below).
• Rows per ear – almost always an even number, typically 14 to 18 for modern hybrids.
• Kernels per row – average number of kernels along one row of the ear, counted from base to tip.
• 90 – the “fudge factorâ€� that converts kernel count to bushels at 15.5% moisture. It represents roughly 90,000 kernels per bushel, though the actual number varies from about 75,000 to 110,000 depending on hybrid and growing conditions.

The result is in bushels per acre (bu/acre) at standard moisture. One bushel of shelled corn weighs 56 pounds at 15.5% moisture.

Worked Example

Using the default values from the calculator:

• Ears per 1/1000 acre = 32
• Rows per ear = 16
• Kernels per row = 35

Step 1: Multiply the three counts together:

32 × 16 × 35 = 17,920 kernels per 1/1000 acre

Step 2: Multiply by 1000 to get kernels per acre:

17,920 × 1000 = 17,920,000 kernels per acre

Step 3: Divide by 90 to convert to bushels:

17,920,000 ÷ 90 = 199,111 … wait, that’s not right. Let’s redo it correctly.

Actually, the formula is (ears × rows × kernels) ÷ 90, with ears already per 1/1000 acre. So:

32 × 16 × 35 = 17,920

17,920 ÷ 90 = 199.1

So the estimated yield is 199.1 bushels per acre, matching the calculator output. The “kernels per acre� output multiplies the product by 1000, giving 17,920,000 kernels per acre.

How to Take the Field Counts

Accuracy depends entirely on how you sample. The standard method:

1. Determine the row spacing of your planter (e.g., 30 inches).
2. Calculate the length of row that equals 1/1000 acre. For 30-inch rows, that is 17 feet 5 inches (30 inches = 2.5 ft; 43,560 sq ft / 2.5 ft = 17,424 ft per acre; 17,424 / 1000 = 17.4 ft). For 36-inch rows, it is 14 feet 6 inches. For 20-inch rows, it is 26 feet 2 inches.
3. At several representative spots in the field, mark that length of row.
4. Count every ear that has at least one harvestable kernel. Do not count nubbins or ears with severe insect damage.
5. Pick every 5th or 10th ear, count the kernel rows (around the ear) and the kernels per row (along one side, from base to tip, excluding the very tip if it’s aborted).
6. Average the rows per ear and kernels per row across all sampled ears.

Take at least 5 to 10 samples across the field, avoiding headlands and wet spots, and average them. The more samples, the better the estimate.

Why the 90 Factor Works (and When It Doesn’t)

The number 90 is a long-standing rule of thumb. It assumes that one bushel of corn contains about 90,000 kernels. That number comes from average kernel weight: a kernel weighs roughly 0.25 to 0.35 grams at 15.5% moisture. A 56-pound bushel is about 25,400 grams, so 25,400 / 0.30 ≈ 84,700 kernels. The 90 factor is slightly conservative, giving a lower yield estimate than the true kernel weight might suggest.

In practice, the factor varies:

• Large, plump kernels (e.g., from a good grain-fill period) may have only 75,000–80,000 per bushel, so dividing by 90 underestimates yield.
• Small, light kernels (e.g., from drought stress) may have 100,000+ per bushel, so dividing by 90 overestimates yield.

Some agronomists use 80 or 85 for high-yield environments, but 90 remains the standard for general estimates. If you want a more precise number, you can weigh a known number of kernels and adjust, but for a quick pre-harvest check, 90 is fine.

Common Mistakes and How to Avoid Them

• Wrong row length: Using 17.4 ft for 30-inch rows is correct, but many people use 17 ft 5 in. That’s fine, but if you use 15 ft, you’ll overcount ears. Always measure your actual row spacing.
• Counting all ears, not just harvestable ones: Ears with no kernels or severe damage should be excluded.
• Not averaging enough ears: Counting kernels on just one or two ears can give wildly wrong results. Sample at least 10 ears per location.
• Ignoring moisture: The formula assumes 15.5% moisture. If you harvest wetter or drier, the weight per bushel changes. Wet corn weighs more per bushel at the same volume, but the standard bushel is always 56 lb at 15.5%.
• Rounding too early: Do the multiplication and division in one step, then round. Rounding intermediate values can shift the result by several bushels.

How to Use the Result

The number you get is an estimate of the dry grain yield at standard moisture, before harvest losses. Actual harvested yield will be lower due to:

• Combine losses (shatter, stalk drop, header loss) – typically 2–5%.
• Grain moisture at harvest – if you harvest at 25% moisture, you’ll lose weight when drying to 15.5%.
• Field variability – your sample spots may not represent the whole field.

Use the estimate to plan storage, drying, and marketing. For crop insurance or sales, you need actual scale tickets. The calculator is a planning tool, not a legal measurement.

Frequently Asked Questions

What is a good corn yield per acre?

In the U.S., the national average is around 175–180 bushels per acre (recent years). Irrigated or high-management fields can exceed 250 bu/acre, while dryland or low-input fields may be under 100. “Good� depends on your region, rainfall, and inputs. Use the calculator to see where your field stands relative to your county average.

How do I convert bushels per acre to tons per hectare?

One bushel of corn at 15.5% moisture weighs 56 lb = 25.4 kg. One bushel per acre = 25.4 kg / 0.4047 ha = 62.8 kg/ha. So multiply bu/acre by 0.0628 to get metric tons per hectare. For example, 200 bu/acre × 0.0628 = 12.56 t/ha.

Why do I count ears per 1/1000 acre instead of per acre?

Counting an entire acre is impractical. A 1/1000 acre sample is a manageable length of row, and multiplying by 1000 gives the per-acre number. It also lets you compare fields with different row spacings on a common basis.

Can I use this calculator for seed corn or silage?

No. Seed corn is sold by weight or count, not bushels, and silage yield is measured in tons of fresh or dry matter per acre. The formula here is for grain corn at standard moisture.

What if my kernel rows per ear is an odd number?

That’s rare but possible, especially at the tip or base. Use the actual count, not an average of even numbers. The formula works with any number, but if you see many odd rows, check your counting method – you might be double-counting.

Does this formula work for popcorn or sweet corn?

No. Popcorn has a different kernel density and moisture standard (usually 13–14.5% moisture, and bushel weights vary). Sweet corn is harvested fresh, not as dry grain. The 90 factor and 56 lb/bushel apply only to field corn.

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in ears | Harvestable ears per 1/1000 acre | ears | 32 | 0 | 100
in rows | Kernel rows per ear | rows | 16 | 8 | 24
in kernels | Kernels per row | kernels | 35 | 5 | 80
out bu | Yield | bu/acre | ears * rows * kernels / 90 | 1
out kac | Kernels per acre | kernels | ears * rows * kernels * 1000 | 0