Order quantity calculator
Order too little and you sell out early; order too much and you’re left clearing stock. This calculator weighs the margin you’d lose on a stock-out against the loss on leftover units to suggest how many to order, and shows how that order holds up if demand comes in weaker or stronger than you expect.
Consider ordering 962 units.
Your numbers
If demand is weak (850 units) you'd sell 850 and still turn a profit; if it runs strong (1,150) you'd sell out and miss about 188 units of demand.
If demand is weaker
Demand 850 units
- Sold
- 850 units
- Left over
- 112 units
- Lost on leftovers
- -£3,360
If demand is as expected
Demand 1,000 units
- Sold
- 962 units
- Short
- 38 units
- Missed margin
- -£760
If demand is stronger
Demand 1,150 units
- Sold
- 962 units
- Short
- 188 units
- Missed margin
- -£3,760
Estimates only, based on the numbers you enter. This models demand as a normal distribution around your estimate and balances the margin lost on a stock-out against the loss on leftover units. It doesn't account for fixed costs, reorders within the window, or the effect of price on demand.
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Apply for fundingOrder quantity calculator FAQ
It weighs two costs against each other: the margin you'd miss on a sale you can't fulfil if you run out, against the loss on any unit left unsold. The quantity it suggests is the point where ordering one more unit is exactly as likely to be wasted as it is to save a lost sale, given how confident you are in your demand estimate.
The newsvendor model is a classic inventory formula for one-shot ordering decisions, buying stock once for a fixed selling window with no reorders, which is exactly the shape of a Black Friday order. It balances the cost of ordering too little (a stockout) against the cost of ordering too much (unsold leftovers) to find the quantity that maximises expected profit. This calculator is a plain-language version of that model.
Stockout cost is the profit you miss on every sale you can't fulfil because you ran out of stock, which this tool takes as your margin per unit. A higher margin makes running out more costly relative to overordering, so the calculator recommends carrying more stock as a buffer.
It sets how wide a range of outcomes the calculator plans around. Fairly sure narrows the spread of likely demand, so the recommended order sits close to your estimate; Could be off a lot widens it, which usually pushes the order quantity further from your estimate to protect against a bigger miss in either direction.
It sets how much you can recover on unsold stock, from Close to cost at one end down to Nothing if it's a genuine write-off. The less you can recover, the more expensive overordering becomes relative to running out, so the calculator recommends a smaller order.
Enter that multiple in Order in multiples of, and the recommendation is rounded to the nearest quantity you can actually order, rather than an exact number your supplier can't fulfil.
Map your order deadline back from sale day with the backwards planner, or check whether financing the extra stock pays for itself with the financing break-even calculator. Browse every tool in the full Black Friday toolkit.