Start with the crop, not the price chart
Onion storage is a quality-control job before it is a speculation on a higher price. A farmer who has harvested during rain, sees neck rot, or has many bruised bulbs faces a very different decision from a farmer with well-cured, sound onions. Select bulbs that are mature and dry enough for the intended storage method. Remove damaged, cut, visibly infected or soft bulbs before loading a store. Do not assume that a quoted later mandi price will apply to a lot that loses grade while it sits. Grading is part of the financial calculation: a saleable quintal of poor-quality bulbs may fetch less than the headline mandi quotation.
Curage, ventilation and a dry start
After harvest, curing dries the outer skins and necks. A wet or thick neck is a route for deterioration; careless handling creates bruises that can rot later. The safe method depends on weather and local varieties, so ask a nearby horticulture extension worker about suitable curing time and handling. Keep harvested bulbs out of standing water and protect them from rain. Before storage, inspect the pile from several points, not only the top. A store full of green, wet or already sprouting bulbs is not rescued merely by a longer waiting period.
NHRDF notes that temperature, humidity and ventilation influence respiration, sprouting, rotting and moisture loss in stored onions. An improved ventilated structure tries to balance air movement with protection from weather. Avoid piling bulbs so tightly that the centre cannot breathe. Keep the floor dry, allow inspection access and follow the store operator's loading plan. Ask who measures intake and outturn weight, how rejects are recorded, and whether the store includes insurance. Even a technically sound structure cannot eliminate losses from a vulnerable lot.
Make four estimates before signing storage terms
Write down today's actual sale price per quintal for your grade and location. Next, collect the full storage charge: monthly rent, handling, loading, unloading, packaging and any minimum charge. Third, estimate the change in saleable quantity, separating moisture and respiration shrinkage from bulbs that become unsaleable. Fourth, record the annual cost of money tied up by not selling today. If the crop is financed, use the relevant borrowing cost. If it is not, consider what you could do with proceeds from an immediate sale. Each number should reflect your own lot and contract rather than somebody else's online example.
The calculator uses an illustrative 5% monthly shrinkage and 1% monthly spoilage as starting scenarios, not claims about average losses. At three months, these rates compound; they are not simply multiplied by three. If your loss estimate already counts rotten bulbs in the total weight loss, set separate spoilage to zero so you do not count the same loss twice. Periodically weigh a small representative sample if practical, while recognizing that a sample may not capture rot hidden in the middle of a large stack.
What price is needed later?
Suppose you hold 100 quintals and can sell at ₹2,000 per quintal today. Today's gross sale would be ₹2,00,000. If three months of rent are ₹80 per starting quintal per month, rent is ₹24,000. At an annual capital cost of 10%, three months of simple opportunity cost add ₹5,000. Extra transport of ₹3,000 would bring cash and capital costs to ₹32,000. This does not yet account for the reduced quantity. If the original 100 quintals fall to about 83.2 saleable quintals after compounded 5% shrinkage and 1% separate spoilage, the later price must exceed roughly ₹2,790 per remaining quintal to match the immediate sale. This example is hypothetical; enter your real figures above.
Notice that storage rent is charged against the initial quantity in this model, while sale revenue is earned on the quantity remaining at the end. That mismatch is why adding a few rupees to today's price is not enough. The break-even number rises sharply when the saleable quantity falls. It rises again when you add extra transport or a higher cost of capital. If your warehouse charges against the remaining quantity or has different billing terms, adjust the rent input into an equivalent charge for the original load.
Check the market, then test a downside case
Before choosing to store, compare several markets and dates on AGMARKNET, and verify recent arrivals and prices with your own buyer or mandi. Historical movements are evidence of volatility, not a forecast. Write down a realistic future price and a conservative one. Run both in the calculator. If storage only works under the most optimistic future price, treat it as a risk, not an assured gain. Consider selling part of the lot now if that better matches your cash needs and storage capacity. The calculator does not decide your household liquidity needs or whether you can absorb a low outturn.
Before the final sale
Confirm the buyer's quality grade, deductions, market fee, transport route and payment timing. Record starting weight, later saleable weight and actual realized net proceeds. Those notes make next season's assumptions stronger than a generic figure online. Keep receipts for storage and handling so you can compare quoted and actual cost. If spoilage accelerates, reassess instead of waiting only because the original plan said three months. A good decision can change when the crop or market changes. Use the tool as a transparent worksheet, and use local expert advice for disease control and storage design.
Sources and further reading: NHRDF onion information; NHRDF post-harvest technology for onions; AGMARKNET official market price portal. These sources explain storage considerations and offer market reports. They do not certify this calculator’s default rates or predict future prices.