Seeding Rate & Plant Density Calculator (seeds/m², kg/ha)
Work out plant density in seeds/m² and the seeding rate in kg/ha from thousand-grain weight and germination, precision-drill spacing and cover crop mix rates.
Plant density and seeding rate: seeds/m², kg/ha and TGW
Seeding density is the number of seeds to sow per m² to reach the target plant density: seeds/m² = target plants ÷ (germination rate × (1 − emergence losses)). The seeding rate follows from the thousand-grain weight: rate (kg/ha) = seeds/m² × TGW (g) ÷ 100. For winter wheat targeting 250 plants/m², with 95% germination, 10% losses and a 45 g thousand-grain weight, you sow 292 seeds/m², i.e. 131.6 kg/ha.
The formulas
- Effective emergence = germination × (1 − losses). Seeds/m² = target density ÷ effective emergence.
- Rate (kg/ha) = seeds/m² × thousand-grain weight ÷ 100 (1 ha = 10,000 m², weight in grams per 1,000 seeds).
- Units or bags = seeds/ha ÷ seeds per unit, shown in "unit" mode only. Seed cost = units × price per unit, or kg ÷ 100 × price per 100 kg, depending on the mode chosen.
- Harvest = yield (100 kg/ha) × area ÷ 10 in tonnes; revenue = yield ÷ 10 × price per tonne; margin = revenue − seed cost. Without a sale price, the tool shows neither revenue nor margin.
- Default prices are indicative French prices in euros: September 2026 sale prices (see the presets below) and €75 per 100 kg of seed in weight mode (an indicative value of the tool). In unit mode no seed price is suggested: enter your own.
Worked example (soft wheat, 25 ha)
Emergence 0.95 × 0.90 = 0.855. Seeds: 250 ÷ 0.855 = 292/m². Rate: 292.4 × 45 ÷ 100 = 131.6 kg/ha, i.e. 3,289 kg for 25 ha. At 75 quintals/ha and €245/t: 187.5 t and €1,838 per hectare. In "100 kg" mode at €75, seed costs €98.68/ha and the margin after seed reaches €1,739/ha. Grain maize at 90,000 plants/ha (9/m², 96% germination, 5% losses, 320 g): 31.6 kg/ha, i.e. 1.97 units of 50,000 seeds per hectare.
Seeding rate by crop with the tool’s default values
The tool’s presets, checked on 22/10/2026 against reference figures from technical institutes (Arvalis, Terres Inovia) and chambers of agriculture in France; values outside the published range were moved towards the middle of that range. Replace the thousand-grain weight and germination rate with those on the seed lot label, and the density with the one in the next table for your sowing date and soil. Effective emergence = germination × (1 − losses): the institutes express losses from seed to plant, so compare them with 100% minus effective emergence, not with the “Losses” field alone.
| Crop | Target plants/m² | TGW (g) | Germination | Losses | Effective emergence | Seeds to sow/m² | Rate (kg/ha) | Units/ha | Source of the preset |
|---|---|---|---|---|---|---|---|---|---|
| Winter Soft Wheat | 250 | 45 | 95% | 10% | 85.5% | 292.4 | 131.6 | – | Arvalis (Normandy factsheet, 2012 PDF): 170 to 210 plants/m² for early sowing, 210 to 250 for late sowing. The preset is therefore a late-sowing level: 292 seeds/m², like the 290 advised for late sowing in Brittany (2025). |
| Durum Wheat | 280 | 50 | 92% | 12% | 81% | 345.8 | 172.9 | – | Arvalis (Provence-Languedoc factsheet, 2012 PDF): 160 to 320 plants/m² depending on sowing date and tillering; 280 matches sowing after 15 December or poor tillering. 81% emergence is close to the 20% losses that are normal in the region. |
| Winter Barley | 230 | 42 | 95% | 10% | 85.5% | 269 | 113 | – | Brittany chamber of agriculture (2025): 230 plants/m² for six-row winter barley, 250 to 265 seeds/m². Previous preset: 240 plants/m². |
| Winter Oilseed Rape | 30 | 5 | 90% | 15% | 76.5% | 39.2 | 2 | 0.26 | Terres Inovia (oilseed rape guide 2024): 20 to 35 plants/m²; 40 seeds/m² and 1.6 to 2 kg/ha with a cereal drill when losses are low; thousand-grain weight of 4 to 5 g. Previous preset: 40 plants/m². |
| Grain Maize / Corn | 9 | 320 | 96% | 5% | 91.2% | 9.9 | 31.6 | 1.97 | Arvalis (02/04/2026): 75,000 to 110,000 plants/ha depending on maturity group. The 98,684 seeds/ha sown stay within the Saône-et-Loire chamber of agriculture range (75,000 to 100,000, 2025). Thousand-grain weight not published by the institute. |
| Sunflower | 5.5 | 60 | 92% | 8% | 84.6% | 6.5 | 3.9 | 0.43 | Terres Inovia (sunflower guide 2025): 55,000 plants/ha under moderate water stress (range 50,000 to 60,000); emergence rate of 75% (general case) to 85% (optimal conditions); units of 150,000 seeds. Previous preset: 7 plants/m² and units of 75,000 seeds. Thousand-grain weight not published. |
| Soybean | 40 | 180 | 90% | 10% | 81% | 49.4 | 88.9 | 3.29 | Terres Inovia (soybean guide 2025, 2019 trial data): 30 to 50 emerged plants/m² depending on maturity group and water stress; 80% emergence in the general case; 180 g thousand-grain weight used by the 2025 soybean guide. Previous preset: 55 plants/m². |
| Field Peas | 70 | 230 | 92% | 12% | 81% | 86.5 | 198.9 | – | Terres Inovia: 70 plants/m² in its example of a spring pea crop yielding 6 t/ha (2019, updated 2025); 86 seeds/m² sown, between the 70 to 80 (loam) and 90 (clay) advised in 2026; 230 g thousand-grain weight. Previous preset: 85 plants/m², i.e. 105 seeds/m². |
Crop presets and limits
- The target densities, emergence rates and thousand-grain weights of the presets are checked against the sources in the table above. The maize thousand-grain weight (320 g) lies within the range of German seed lots from 2011 to 2018 (224.9 to 353.0 g from the 5th to the 95th percentile, mean 289.8 g) and the sunflower one (60 g) matches their mean (60.3 g), according to the Julius Kühn-Institut (Heimbach, Journal für Kulturpflanzen, 2018). The expected yield and the seeds per unit for oilseed rape (1.5 million) and soybean (150,000) remain unsourced starting values. The weight and germination rate are printed on the seed lot label, and density depends on sowing date and soil condition.
- Wheat, barley and peas are usually bought by weight: the tool opens in, and switches these crops to, "100 kg" mode. Rapeseed, maize, sunflower and soybean switch to "unit" mode with the preset's seeds per unit; if you pick "unit" mode for a crop sold by weight, the tool counts units of 500,000 seeds. Switching mode resets the seed price to its default: €75 per 100 kg, or 0 in unit mode.
- Default sale prices: September 2026 average quotes published by La Dépêche and reported by Agreste Île-de-France, Conjoncture no. 10 (October 2026, checked 28/10/2026): milling soft wheat €245/t and milling barley €224/t delivered Rouen, maize €273/t delivered Bordeaux (harvest year not stated), oilseed rape €546/t delivered Rouen, sunflower €551/t delivered Bordeaux. These port-delivered prices are above the price paid to farmers: ex-farm Eure-et-Loir, wheat and barley were quoted €7 to €11/t lower. Durum wheat, soybean and peas: no verified quote, enter your sale price.
- The margin only deducts seed: fertiliser, crop protection and machinery are not included.
Target seeding densities by crop (French references)
These figures come from technical institutes and chambers of agriculture in France; they vary with region, soil and variety. Density changes with sowing date for cereals, and with the season for peas and faba beans. For oilseed rape, Terres Inovia sets density by soil, row spacing and emergence losses. For maize, maturity group, yield potential and irrigation are what count; for sunflower, water stress. Enter the chosen density in the “Target density” field, then the thousand-grain weight and germination of your seed lot. “Not published”: the source only gives seeds to sow.
| Crop | Target plants | Seeds to sow (by sowing date, soil or the source’s criterion) | Source |
|---|---|---|---|
| Winter soft wheat | 220 plants/m² at the end of winter for a late-October sowing (Brittany). Arvalis: 170 to 210 for early sowing, 210 to 250 for late sowing. | Late-October sowing in good conditions: 240 to 250 seeds/m². Late sowing: 290 seeds/m². After 10 November, add 1% to expected losses per day of delay. | Chambre d’agriculture de Bretagne, 16/10/2025 (updated 12/03/2026); Arvalis, Normandy factsheet (2012 PDF) |
| Durum wheat | By sowing date, with good tillering: 160 plants/m² from 5 to 25 October, 200 from 25 October to 15 November, 240 from 15 November to 15 December, 280 after that. Add 40 plants/m² if tillering is poor. | For 20% losses, the regional norm: 200, 250, 300 and 350 seeds/m² (250, 300, 350 and 400 with poor tillering). | Arvalis, Provence-Languedoc factsheet (2012 PDF) |
| Six-row winter barley | 230 plants/m² | 250 to 265 seeds/m²; 310 for late sowing | Chambre d’agriculture de Bretagne, 2025 (updated 2026) |
| Two-row winter barley | 260 plants/m² | 285 to 300 seeds/m²; 350 for late sowing | Chambre d’agriculture de Bretagne, 2025 (updated 2026) |
| Winter oilseed rape | 20 to 35 plants/m² in autumn: 25 to 35 on deep soil, 30 to 35 on shallow soil (15 to 34 cm rows). No density by sowing date: Terres Inovia asks for emergence before 1 September, to reach 4 leaves before 20 September. | Cereal drill (15 to 34 cm): 40 seeds/m² with low emergence losses (≈ 15%), 50 with moderate losses (≈ 30%), 55 with high losses (≈ 40%). Precision drill at 45-50 cm: 30, 40 and 45. | Terres Inovia, oilseed rape crop guide 2024; note on triggering rapeseed sowing, 04/08/2025 |
| Grain maize | Plants at harvest by maturity group (75 to 80 cm rows): very early G0, 100,000 to 110,000/ha; early G1, 95,000 to 105,000 (flint or flint-dent) or 85,000 to 100,000 (dent); G2, 85,000 to 95,000; G3, 80,000 to 90,000; G4, 75,000 to 85,000. Increase for emergence losses. | By maturity group and potential: early G1, 90,000 seeds/ha on capping loams (8 to 9 t/ha) to 100,000 on irrigated soil (11 to 12 t/ha); medium-late G4, 75,000 to 80,000. That is 7.5 to 10 seeds/m². | Arvalis, 02/04/2026 (Centre, Île-de-France, Auvergne); Chambre d’agriculture de Saône-et-Loire, January 2025 |
| Sunflower | By water stress: 50,000 plants/ha (severe), 55,000 (moderate), 60,000 (low, rows under 60 cm; 50,000 to 55,000 with wide rows). That is 5 to 6 plants/m². | At the indicative 75% emergence rate: 65,000, 70,000 and 75,000 to 80,000 seeds/ha. Under optimal emergence conditions (85%): 60,000, 65,000 and 70,000. | Terres Inovia, sunflower crop guide 2025 |
| Soybean | By maturity group and water stress: 50 emerged plants/m² for groups 000 and 00 (40 for a 00 without water stress), 40 for groups 0 and I-II, 30 for those groups without water stress. | 80% emergence (general case): 65, 50 or 40 seeds/m². Optimal emergence (90%): 55, 45 or 35. | Terres Inovia, soybean crop guide 2025; soybean stand page, 25/04/2019 (updated 16/12/2025) |
| Winter peas | Trial reference: 60 plants/m² on loamy soil (Terres Inovia trials 2015-2018) | 70 to 80 seeds/m² on loamy soils; 80 to 90 on clay or stony soils | Terres Inovia (Terre-net, 14/10/2021); SEMAE technical day, 13/03/2019 |
| Spring peas | Reference: 70 plants/m² in the example of a 6 t/ha crop; below 50 plants/m², density is low. | 70 to 80 seeds/m² on loamy soils; 90 on clay or stony soils; 105 on chalk soils, for 90% germination and a 230 g thousand-grain weight | Terres Inovia, 14/01/2026; spring pea yield page, 2019 (updated 2025) |
| Winter faba bean | Not published | 20 to 25 seeds/m² on loamy soils; 30 on clay or stony soils | Terres Inovia (Terre-net, 14/10/2021) |
| Spring faba bean | Not published | 40 to 45 seeds/m² on loamy soils; 45 to 50 on clay or stony soils, for 90% germination; 5 seeds/m² fewer with a precision drill. | Terres Inovia, 14/01/2026 |
Precision drilling: row spacing, in-row spacing and seeds/ha
One hectare is 100,000,000 cm². Seeds/ha = 100,000,000 ÷ (row spacing × in-row spacing, in cm), and seeds per metre of row = 100 ÷ in-row spacing. Maize at 75 cm rows and 14 cm in the row: 95,238 seeds/ha, i.e. 9.5 seeds/m² and 7.1 seeds per metre. Sugar beet at 45 cm and 18 cm: 123,457 seeds/ha. The other way round, spacing = 100,000,000 ÷ (row spacing × seeds/ha): 70,000 sunflower seeds/ha at 60 cm rows means one seed every 23.8 cm. The tool also gives the spacing matching the seeds/ha calculated at the top of the page. Terres Inovia describes 45-50 cm rows as “beet or sunflower type”, 60 cm as “sunflower type” and 70-80 cm as “maize type” (oilseed rape guide 2024).
Seeding rate for a cover crop or catch crop mix
Terres Inovia (technical factsheet on cover crops in south-western France, 2024) works out each species’ rate as: rate in the mix = rate of the species sown alone × its intended percentage of the mix. The factsheet’s example, with four species at 25%: faba bean 180 kg × 0.25 = 45 kg/ha, hairy vetch 40 × 0.25 = 10 kg/ha, Chinese radish 8 × 0.25 = 2 kg/ha and phacelia 8 × 0.25 = 2 kg/ha, i.e. 59 kg/ha of mix (1,475 kg for 25 ha). The ratio of a species’ rate in the mix to its pure-stand rate is its share, and these density ratios add up to 100%. The tool shows the sum and flags it when it is not 100%, without blocking the calculation. Example: with 40% faba bean, 30% vetch and 20% each of radish and phacelia, the sum reaches 110% and the rate 87.2 kg/ha.
Frequently Asked Questions
How do I calculate a seeding rate in kg/ha?
Multiply the number of seeds to sow per m² by the thousand-grain weight in grams, then divide by 100. With 292 seeds/m² and a 45 g weight, the rate is 131.6 kg/ha.
How many seeds should I sow to get 250 plants/m²?
Divide the target density by the effective emergence rate. With 95% germination and 10% losses, the rate is 0.855: you need to sow 292 seeds/m².
What is thousand-grain weight (TGW)?
The weight of 1,000 seeds in grams, shown on the seed lot label. It changes the rate a lot: at the same density, wheat at 50 g needs 146.2 kg/ha against 131.6 kg/ha at 45 g.
How many units of maize seed per hectare?
For 90,000 plants/ha with 96% germination and 5% losses, the tool counts about 98,700 seeds/ha, i.e. 1.97 units of 50,000 seeds. A 25 ha field therefore needs 50 units.
What TGW and seeding rate for oilseed rape?
The tool starts from 30 plants/m², a TGW of 5 g, 90% germination and 15% losses: you need to sow 39 seeds/m², or 2 kg/ha. Terres Inovia (2024) targets 20 to 35 plants/m² and advises 40 seeds/m² with a cereal drill when emergence losses are low. The actual TGW is on the seed lot label; at 6 g, the rate rises to 2.4 kg/ha.
What seeding density for winter wheat?
The Brittany chamber of agriculture (2025) targets 220 plants/m² at the end of winter: 240 to 250 seeds/m² for a late-October sowing in good conditions, about 290 seeds/m² for late sowing. After 10 November, it adds 1% to expected losses per day of delay.
How do I convert row spacing and in-row spacing to seeds/ha?
Divide 100,000,000 by the row spacing multiplied by the in-row spacing, both in centimetres. At 75 cm rows and 14 cm in the row, you sow 95,238 seeds/ha, i.e. 9.5 seeds/m².
How do I calculate the seeding rate of a cover crop mix?
Multiply each species’ pure-stand rate by its share of the mix. With 25% each of faba bean (180 kg/ha alone), hairy vetch (40), Chinese radish (8) and phacelia (8), you sow 45 + 10 + 2 + 2 = 59 kg/ha (Terres Inovia example, 2024).
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