Reorder Point Calculator
When to reorder inventory.
Calculate your inventory reorder point using daily usage rate, supplier lead time, and safety stock days to avoid stockouts.
What this tool does
This calculator estimates the inventory level at which a new order should be placed based on usage patterns and supply delays. It combines the demand expected during the lead time—the period between placing an order and receiving stock—with a safety buffer to account for variability in usage or delivery. The result represents a threshold quantity: when inventory falls to this point, reordering begins. The calculation responds most to changes in daily usage rate and lead time length; longer delays or higher consumption both raise the reorder point. A retailer managing seasonal products or a manufacturer with variable demand might use this to balance avoiding stockouts against holding excess inventory. The calculator assumes usage rates remain relatively stable and does not account for factors like demand spikes, supplier reliability changes, or storage constraints.
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Formula Used
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Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
Reorder point is the inventory level that triggers a new order. Formula: (daily usage × lead time) + safety stock. If you sell 100 units/day and lead time is 14 days, you need 1,400 units on hand when the reorder triggers, plus safety stock for demand variability. Running out before reorder arrives = stockout; ordering too early = excess carrying cost.
50 units/day average × 10-day lead time = 500 lead-time demand. + 7 days safety stock × 50 = 350. Reorder point = 850 units. When inventory hits 850 units, place the order. Inventory should arrive when stock reaches ~350 (safety stock buffer), giving protection against demand spikes or delivery delays.
Safety stock calibration: too little = frequent stockouts, lost sales, customer frustration. Too much = wasted carrying cost on rarely-used buffer. Statistical approach: safety stock = z-score × standard deviation of demand × √lead time. Most businesses set safety stock at 1-2 standard deviations (84-97.7% service level).
Quick example
With avg daily usage of 50 and lead time of 10 (plus safety stock of 7), the result is 850 units. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.
Which inputs matter most
You enter Avg Daily Usage, Lead Time (days), and Safety Stock (days). Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.
What's happening under the hood
Lead-time demand = daily usage × lead time. Safety stock = daily usage × safety days. Reorder point = lead-time demand + safety stock. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.
What the score tells you
Headline financial numbers — income, savings, debt — each tell part of the story. This calculation stitches several together into a single read you can track over time. The value is in the direction, not the absolute number.
What this doesn't capture
The score is a composite of the inputs you provide. Life context — job security, family obligations, health, housing — doesn't appear in the math but shapes the real picture. Use the number as a prompt, not a verdict.
50/day × 10 days + 7 safety = 850 units.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
The calculator computes reorder point by multiplying average daily usage by lead time in days, yielding the lead-time demand—the quantity consumed during the replenishment cycle. It then calculates safety stock by multiplying average daily usage by the safety stock buffer period in days. The reorder point is derived by adding lead-time demand and safety stock together. This approach assumes daily usage remains constant, lead time does not vary, and safety stock adequately covers demand uncertainty during the replenishment window. The model does not account for demand variability, lead-time fluctuations, seasonal patterns, stockout costs, or holding costs. It treats usage and timing as deterministic inputs rather than probabilistic distributions.
References
Frequently Asked Questions
How much safety stock?
Lead time varying?
What about seasonal demand?
Automated reorder systems?
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