Compost & Manure Calculator & Quantity & NPK Credit
Works out how much FYM
Find exactly how much compost, farmyard manure, vermicompost or poultry manure to apply — over a field (area × rate) or a garden bed (area × depth) — in tonnes, loads and bags, plus the N-P-K credit it supplies.
Apply about 6.07 tonnes (6,070 kg, ~3.04 trolley loads or 152 bags) of farmyard manure (fym) over 1 acre. That alone supplies roughly 30 kg N, 15 kg P₂O₅ and 30 kg K₂O — subtract this from your fertilizer plan.
Next: spread evenly and incorporate into the soil 2–3 weeks before sowing so it part-decomposes. Well-rotted manure is safer than fresh; fresh manure can burn roots and carry weed seeds.
Nutrient values are typical averages — actual content varies with source, age and moisture. Only a fraction of N is available in year one.
Compost & manure — key facts
- FYM field rate
- 10–20 t/ha (4–8 t/acre)
- FYM nutrients
- ~0.5% N · 0.25% P₂O₅ · 0.5% K₂O
- Compost
- ~1% N · ~650 kg/m³
- Vermicompost
- ~1.6% N · used at ≤5 t/ha
- Poultry manure
- ~3% N · used at low rate
- Trolley load
- ≈ 2 tonnes
- Garden top-dress
- 2–5 cm spread depth
- Privacy
- Runs in your browser; nothing uploaded
How the quantity is worked out
In Field mode, the tool multiplies your area (converted to hectares) by the application rate in tonnes per hectare to get the total quantity, then expresses it in kilograms, ~2-tonne trolley loads and 40 kg bags. In Bed mode, it multiplies area by the spread depth to get a volume, then uses each material's bulk density to convert that to weight — handy for raised beds and top-dressing.
Either way it also reports the nutrient credit: total nitrogen, phosphate and potash supplied, from each material's typical fresh-weight content. Because organic matter releases nutrients slowly, only a portion of the nitrogen is plant-available in the first season — so treat the credit as a reason to trim, not eliminate, your fertilizer dose.
Field application
Enter acres, hectares or bigha and a t/ha rate to get the tonnes, trolley loads and bags to cart out.
Raised beds & gardens
Switch to Bed mode and give a spread depth in cm to get volume, weight and bags for top-dressing.
Nutrient credit
See the N-P-K your manure supplies and deduct it from your fertilizer plan to save on inputs.
Budget the cost
Add a price per tonne to estimate what the manure will cost for the whole area, in your currency.
Frequently Asked Questions
How much manure should I apply per acre?+
Farmyard manure is commonly applied at 10–20 tonnes per hectare (about 4–8 tonnes per acre) for general field crops; richer materials like vermicompost or poultry manure are used at lower rates (5 t/ha or less). This tool converts any rate to the exact quantity for your area in tonnes, kilograms, trolley loads and bags.
How do I calculate compost for a garden bed?+
Switch to Bed mode, enter the bed area and the spread depth in centimetres, and the tool multiplies area × depth to get the volume, then uses the material's bulk density to give the weight and number of bags. A 2–5 cm top dressing is typical for established beds.
How much compost is 5 cm over 10 m²?+
Five centimetres over 10 m² is 0.5 m³ (500 litres). At a compost bulk density of about 650 kg/m³ that's roughly 325 kg — around nine 40 kg bags. Use Bed mode to compute it for your own area and depth.
What NPK does farmyard manure supply?+
FYM averages about 0.5% N, 0.25% P₂O₅ and 0.5% K₂O on a fresh-weight basis, so 15 tonnes supplies roughly 75 kg N, 37 kg P₂O₅ and 75 kg K₂O. The tool shows this nutrient credit so you can reduce your chemical fertilizer accordingly. Note that only part of the nitrogen is available in the first season.
Is poultry manure stronger than cow manure?+
Yes — poultry manure is much more concentrated (around 3% N) than fresh cow dung (~0.4% N), so it's used at far lower rates and must be well-composted to avoid burning crops. The calculator carries the right nutrient content for each material.
How many trolley loads of manure is that?+
A standard tractor trolley holds roughly 2 tonnes of manure, so the tool divides the total tonnage by 2 to estimate loads. Your trolley may differ — treat it as a planning guide.
Should I use fresh or well-rotted manure?+
Use well-rotted or composted manure where possible. Fresh manure is high in ammonia and can scorch roots, carries weed seeds and pathogens, and ties up nitrogen as it decomposes. Apply and incorporate 2–3 weeks before sowing.
Can I subtract this from my fertilizer dose?+
Yes — the nutrient credit shown can be deducted from your recommended NPK, then converted to bagged fertilizer with our Fertilizer (NPK) Calculator. Because manure releases nutrients slowly, credit only a portion of the nitrogen in year one.
What is the bulk density used for volume?+
Each material has a typical bulk density (FYM ~800, compost ~650, vermicompost ~700, poultry ~900 kg/m³). The tool uses these to convert between weight and volume, so Bed mode and the volume figure are realistic for loose, moist material.
Does this replace a soil test?+
No — it estimates how much to apply and the nutrients it adds, but it can't tell you what your soil already has. Pair it with a soil test and our soil and fertilizer tools for a complete nutrient plan.