TGW Seed Rate & Precise kg/ha
Sows wheat
Work back from the plant stand you want using your lot's thousand-grain weight and germination to get a precise seed rate in kg/ha and kg/acre, seeds per m² and the total seed for your area.
Your seed lot & stand
Next: use your seed lot's tested TGW and germination on the bag; if drilling vs broadcasting, raise establishment losses for broadcast.
TGW and germination are lot-specific — read the seed tag; establishment depends on seedbed, moisture and method.
TGW seed rate — key facts
- Seeds/m²
- target plants ÷ (germ × estab × purity)
- Seed rate
- seeds/m² × TGW(g) ÷ 100
- TGW
- weight of 1000 seeds
- Germination
- from the seed tag
- Establishment
- 70–95%, field losses
- Broadcasting
- lower establishment than drilling
- Why TGW
- beats a generic kg/acre figure
- Privacy
- Runs in your browser; nothing uploaded
Sow by the stand you want, not by a rule of thumb
Seed is sown by number of plants but bought by weight, and a generic kg/acre figure hides that gap. Two bags of the same crop can have very different seed sizes and germination, so the same weight gives very different stands — too thin and you lose yield, too thick and you waste expensive seed. The right way is to start from the plant population you want, then convert it to kilograms using your own lot's thousand-grain weight and germination.
This tool does exactly that: seeds/m² from your target stand divided by germination, establishment and purity, then a precise seed rate in kg/ha and kg/acre, seeds per m² and the total seed for your field. Drop the establishment factor for broadcasting versus drilling, use the germination off the tag, and you'll order and sow the right amount for once. Pair it with the Seed Rate, Plant Stand Count and Germination Test tools to plan the crop from the ground up.
Hit your target stand
Back-solve the rate from the population you want.
Use your real lot
TGW and germination beat book averages.
Don't waste seed
Avoid sowing too thick on costly seed.
Adjust for method
Higher rate for broadcasting than drilling.
Frequently Asked Questions
How is the seed rate calculated from TGW?+
You work back from the plant stand you want. First, seeds/m² = target plants/m² ÷ (germination × establishment × purity, all as fractions). Then seed rate (kg/ha) = seeds/m² × thousand-grain weight (g) ÷ 100. So a heavier seed, lower germination or higher field losses all push the kilograms per hectare up — the tool does it precisely for your lot.
What is thousand-grain weight (TGW)?+
TGW is the weight in grams of 1000 seeds — sometimes called thousand-kernel weight. It captures how big and heavy your particular seed lot is, which varies by crop, variety and season. Because seed is sown by number of plants but bought by weight, TGW is the bridge between the two, and using your lot's actual TGW beats any generic kg/acre rule.
Why is this better than a generic kg/acre figure?+
A blanket kg/acre recommendation assumes an average seed size, germination and field loss. Your lot may have larger seeds, a lower germination on the tag, or more establishment loss in your conditions. Calculating from your seed's real TGW and germination gives the right weight to hit your target stand — no thin or wasteful crops.
Where do I find germination and TGW?+
Germination is printed on the seed tag or certificate as a percentage, from a standard lab test; TGW you can measure by counting and weighing 1000 seeds (or weigh 100 and multiply by ten). Many certified seed lots also state TGW. Use the actual figures for your bag rather than book values for the crop.
What is the establishment factor?+
Germination is measured in ideal lab conditions; in the field, some viable seeds still fail to become plants because of crusting, depth, pests, moisture or weather. The establishment factor (often 70–95%) accounts for that gap. Multiply germination by establishment to get the share of sown seeds that actually become established plants.
Why do broadcasting and drilling differ?+
Drilling places seed at a controlled depth and spacing, so establishment is high and even. Broadcasting scatters seed on the surface where more is eaten, dries out or lands too shallow or deep, so establishment losses are higher. Use a lower establishment factor for broadcasting, which the calculator turns into a higher seed rate to compensate.
What is seed purity and how does it affect the rate?+
Purity is the share of the lot that is pure crop seed rather than chaff, weed seed or inert matter, shown on the tag as physical or pure-seed percentage. Lower purity means fewer real crop seeds per kilogram, so the rate must rise. The tool includes purity in the denominator so impure lots are sown at the right weight.
What target plant population should I aim for?+
It depends on the crop and conditions — for example tens of plants per m² for cereals and fewer for widely spaced row crops. Use the agronomic recommendation for your crop and region as the target plants/m². The calculator then back-solves the seed rate needed to reach that stand given your lot's qualities.
Does it work for any crop or area unit?+
Yes — the TGW method is universal across cereals, pulses, oilseeds and grasses. Enter your crop's target population, the seed lot's TGW, germination, establishment and purity, and the area you're sowing. The tool reports kg/ha, kg/acre, seeds/m² and the total seed for your field.
Are the results exact?+
They're a precise calculation from the numbers you enter, but real establishment depends on seedbed quality, sowing depth, moisture, weather and pests. Treat the rate as an accurate starting point, keep some buffer for gap-filling, and check your stand after emergence to fine-tune the establishment factor for next season.