Economic order quantity
Wilson model: steady annual demand, instant replenishment, no shortages and no quantity discounts. Compare the neighboring whole quantities and the annual costs.
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- Check before download
Wilson model: steady annual demand, instant replenishment, no shortages and no quantity discounts. Compare the neighboring whole quantities and the annual costs.
Calculations run locally and inputs are not saved automatically. Download an input backup before closing the tab. Input data, formulas and filenames are never sent. Only with your optional consent, Refentra sends aggregate counts of actions and outcomes, without input content.
What are the limits?
Maximum amount 1 trillion units; total 100 trillion cents. Up to 100 rows, 50 people, 20 tiers, 100 depreciation years, 1,200 schedule periods, 61 cash flows. IRR range −99% to 1,000% per interval, numerical candidates only. Rates: up to eight decimals. Backup: 1 MiB. CSV formula-leading text gets an apostrophe. Use decimal points, no thousands separators.
Amounts use two decimals in your stated unit. Exact decimal inputs; cent rounding half away from zero. Table sums balance. Largest fractional remainders receive shared cents; equal remainders use row order. No tax, fees, legal entitlement or current prices are inferred.
Non-monetary values are shown with up to ten significant digits. CAGR, fractional-year inflation and IRR use numerical approximations; IRR candidates are not a symbolic proof. CSV keeps the numeric values before display rounding.
Q* = √(2DS/H); K(Q) = DS/Q + HQ/2
Calculate with your own assumptions
- Enter the inputs
Enter the annual demand in units, the ordering cost per order, and the annual holding cost per stored unit. Keep both costs in the same currency and on an annual basis. Enter decimals with a point and without thousands separators.
- Check a worked example
D=1000 units/year, S=10/order, H=2/unit/year: √(2×1000×10/2)=100 units. Ten orders a year cost 100; holding the average stock costs 100; the combined annual cost is 200.
- Interpret and save the result
The continuous optimum is compared by cost with the two whole quantities on either side of it, and the cheaper one is selected. The CSV curve shows ordering and holding costs separately.
Method, errors and limits
Can I reopen editable inputs from the CSV?
The CSV is a report of the results, not a backup of your inputs. Download the separate JSON input backup before you close the page, then import it into this same tool to edit your assumptions again. Import accepts files up to 1 MiB and checks that the file belongs to this tool. Inputs are not saved automatically.
Which input mistakes should I check?
Demand, ordering cost and holding cost must all be positive. Holding cost is an amount of money per unit per year, not a percentage. If you have a percentage, convert it to that amount before you enter it.
What are this model’s limits?
A constant demand and cost model, without shortages, lead times, safety stock or quantity discounts. The optimum can't exceed 1 e 9 units. The tool doesn't order any stock for you.