Define “break even” before calculating
The break-even later price is the price per saleable quintal at the end of storage that makes your net proceeds equal to selling the original lot today. It is not the future market price and it is not your profit target. This definition matters because rent applies to the original load while you can only sell what survives. If you sold today, today's gross proceeds would be starting quantity multiplied by today's price. If you store, you have later sale proceeds less rent, additional transport and the cost of waiting for payment. Set those two sides equal and solve for the later price.
Write the calculation in five steps
First, write starting quantity Q in quintals and today's price P in rupees per quintal. Immediate sale value is Q × P. Second, estimate monthly proportional weight shrinkage s and extra monthly spoilage rate d as decimals. After m months, saleable quantity is Q × (1−s)m × (1−d)m. Third, calculate storage rent as starting Q × monthly rupees per quintal × m. Fourth, calculate the simple opportunity cost on Q × P at annual rate r for m/12 of a year. Fifth, add extra later transport that you would not pay if selling today. The break-even later price is the sum of immediate sale value and these costs divided by remaining saleable quantity.
Algebraically: B = [QP + Qcm + QP(rm/12) + T] / [Q(1−s)m(1−d)m], where c is monthly rent per original quintal and T is extra later transport. The formula assumes no recurring fees beyond rent, equal grade except for unsaleable loss, and simple rather than compounded interest. If you have other costs such as bagging or commission charged only later, add them to T after converting to a total rupee amount. If the future grade receives a lower price than the quoted market rate, use the lower price in your scenario.
A worked example with round inputs
Take 100 quintals at ₹2,000 per quintal now, so the immediate gross value is ₹2,00,000. Suppose monthly rent is ₹80 per starting quintal for three months, monthly shrinkage is 5%, extra spoilage is 1%, annual opportunity cost is 10%, and extra later transport is zero. Rent is ₹24,000 and interest is ₹5,000. Saleable quantity becomes 100 × 0.95 cubed × 0.99 cubed, about 83.2 quintals. The later sale needs to earn ₹2,29,000 across those remaining quintals, so break-even is about ₹2,752 per saleable quintal. Rounding can change the last rupees. The values are only a demonstration; they are not average mandi rates or loss measurements.
At an expected later price of ₹2,600, those 83.2 quintals produce roughly ₹2,16,300 before rent and interest. Deduct ₹29,000 and later net is about ₹1,87,300, below today's ₹2,00,000. At ₹2,900, the sale produces about ₹2,41,300 before charges, so later net is about ₹2,12,300. The higher market price produces a gain in this hypothetical case, but the future market and crop quality may differ. Run the calculator rather than copying rounded example figures into a sale decision.
Why the straight-line shortcut can mislead
A shortcut might add rent and interest per original quintal to today's price and then add an estimated shrinkage percentage. That can be useful for a quick mental check, but it does not properly account for compounding or the shrinking quantity across which costs must be recovered. At small losses, the difference might be modest; at high losses over many months, it can become significant. Keep shrinkage and spoilage separate only when they represent different losses. If one number already includes the other, entering both will make break-even too high.
What the model leaves out
Actual farm accounting may include costs before today's sale that are common to both choices. Common costs cancel in this comparison, but costs that differ between the two routes must be included. The calculator has only one field for extra later transport and uses the current price as the basis for interest. It does not model taxes, commissions, changing grades, fees based on realized price, insurance payouts, different harvest dates or a loan's compounding schedule. Convert a differing cost to an approximate total or consult an accountant for a larger commitment. Do not mistake a clear formula for certainty about uncertain inputs.
Use real records to improve assumptions
Keep a record of intake weight, marketable outturn, invoices and actual sale proceeds. Divide the money received net of later costs by starting quantity to see the real return on the original crop. Compare this with the amount you could have received at the starting date. That review is more informative than remembering only the final price per surviving quintal. For the current mandi quotation, use AGMARKNET as one reference and confirm with buyers and your own grade. Recalculate if loss or local prices change. The decision is live until the lot is sold.
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.