Enter the application rate from your fertiliser or other product label and your lawn area to work out the amount for that area. This tool does not choose a product or a rate; follow the label you have.
Product labels quote a rate per a fixed area, commonly per 100 m² or per hectare (10,000 m²), because that's a convenient round number for the label to print, not because it matches your lawn. A home lawn is typically somewhere between 40 m² and 400 m², rarely a round number and rarely a neat fraction of the label's own area unit. Scaling the label's rate to your actual measured area, rather than eyeballing a fraction of the printed number, is what tells you the real amount for the ground you're treating.
The same problem shows up whichever direction the mismatch runs. A 30 m² garden bed treated with a rate meant for a 100 m² area needs less than a third of the printed figure, scaled down, not the printed figure itself. A 350 m² back lawn treated with the same 100 m² rate needs three and a half times it. Mental arithmetic on an awkward area, or rounding it to "close enough" to the label's own unit, is exactly the guesswork this tool replaces with the actual scaled figure.
A label states 15 g per 100 m². For a 500 m² lawn, that scales to 75 g (500 ÷ 100 × 15), shown alongside its paired scale, 0.075 kg, since either figure might be the easier one to weigh out depending on your scales.
Some rates land on a much smaller figure once scaled down to a small area. A label stating 0.5 kg per hectare applied to a 20 m² garden bed scales to 0.001 kg, a number most kitchen scales can't read meaningfully. The paired scale shows the same amount as 1 g, the figure you'd actually measure. Both come from the same unrounded amount: this tool works out the scaled quantity first and only then rounds each scale for display, so a small result keeps its leading digit instead of rounding away before the second scale is worked out.
The denominator is whatever area the label states its rate "per". Multiplying by your measured area, divided by this figure, scales the rate to your ground.
| Label says "per" | Area this equals |
|---|---|
| 1 m² | 1 m² |
| 10 m² | 10 m² |
| 100 m² | 100 m² |
| hectare | 10,000 m² |
The result is also shown on a paired scale, converted at the same unrounded precision. Which scale it pairs with isn't fixed: if your entered unit's own figure already reads as a plain number between 1 and 1000, it pairs with the next scale as usual; a much smaller or much larger figure instead walks along the same scale toward a scale that does read that way, landing on whichever scale gets closest even on the rare result too small or too large for any scale on the axis to fully manage it, rather than always pairing one fixed step away.
| Axis | Scales, largest to smallest |
|---|---|
| Mass | kg → g → mg |
| Volume | L → mL |
mL is the smallest volume scale this tool uses: a result already under 1 mL has no smaller home-usable unit to pair with, so it's shown alone. The same applies at the largest scale on either axis (kg, L) for a result of 1000 or more.
Applying less than the label's rate across your measured area under-treats whatever the product is meant to fix, weeds, disease or a nutrient gap keep going because the ground never got the amount the label assumes. Applying more than the rate over-treats it, more product spread over the same ground than the label calls for. An area that wasn't actually measured, or a rate that wasn't actually scaled to it, can produce either mistake, though they're not the only ways a wrong quantity ends up applied. Often the mistake isn't obvious on the day, the effect of an under- or over-scaled rate can take time to show up in how the treated area responds, rather than anything visible at the time of application.
A rate scaled to a small or large area can land on a number that's awkward to read in the unit you entered. The second figure is the same unrounded amount on the nearest mass (kg/g/mg) or volume (L/mL) scale, walking further along that scale for a very small or very large result to get as close as it can to a plain number between 1 and 1000, rather than always pairing one fixed step away. A result already under 1 mL, or already at 1000 or more on the largest scale (kg, L), has no better scale to pair with and is shown alone.
This tool covers mL, g, L or kg, per 1 m², 10 m², 100 m² or hectare. If your label uses an imperial unit, convert it to one of these forms first, this tool does not do that conversion for you. A rate per litre of water (a dilution, not a per-area rate) is a different kind of number entirely, it needs your sprayer's actual water output to turn into a per-area amount, which a unit conversion alone can't give you. Use the Sprayer Calibration tool instead, its "Per litre of water" mode is built for exactly that.
Yes. Toggle to "Length × width" and enter the two measurements; the tool multiplies them into a total area the same way the direct-entry option works.
No. The tool works out the scaled quantity first and rounds only for display, in both scales, so a small but real amount keeps its leading digit instead of rounding away to zero.
No. It's free, with no sign-up and no login.
No. It only scales a rate you enter from your own product's current label to your measured area. Always follow label directions and any relevant permit conditions.
A Free LawnSuite account lets you save your lawn zones and calculate a single-product dose from the label rate you enter and your saved zone area, with a weather outlook and treatment log. My Shed products and saved label rates require Pro. Copy this result before leaving; creating an account does not transfer this calculation.
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