Restock Calculator
See when you'll run out, your reorder point, and a suggested reorder quantity — so a slow supplier never leaves you empty-shelved.
- Free calculator
- Instant estimate
- No signup needed
- Beginner friendly
Leave blank for a suggested quantity.
Days until stockout
20.0
Reorder point
50
Reorder when inventory hits this
Suggested reorder quantity
50
Inventory after lead time
40
Short example
Selling 4 units/day with a 10-day lead time and 10 units safety stock puts your reorder point at 50 units. With 80 in stock you have ~20 days before you should reorder.
All calculations are estimates based on average platform fees. Real profits may vary depending on category, ads, and shipping.
Reorder timing is a planning estimate based on the sales velocity and lead time you enter. Real demand and supplier delays vary.
Free worksheet for your next step
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How to use this calculator
- Enter your numbers in each field above — the calculator updates instantly as you type, so there's nothing to submit.
- Use your real figures when you have them, or sensible estimates while you're planning. If a field doesn't apply, leave it at zero.
- Compare the results, then change one input at a time to see how each lever (price, cost, fees, volume) moves the outcome.
When to use this calculator
- When you need to decide whether to reorder now or wait.
- Before a busy season, when sales velocity is about to rise.
- After a supplier delay, to reset your reorder point with the new lead time.
- When planning cash — reorder timing decides when the money leaves your account.
Formula
Days until stockout = Current inventory ÷ Daily sales · Reorder point = Daily sales × Lead time + Safety stock · Reorder now if current ≤ reorder point
Worked example
80 units in stock, 4 units/day, 10-day lead time, 10 safety stock.
- Days until stockout = 80 ÷ 4 = 20
- Reorder point = 4 × 10 + 10 = 50
- 80 > 50, so no need to reorder yet
Answer: 20 days of stock; reorder when it hits 50 units
How it works
Stockouts kill momentum — reviews slow, ads pause, algorithms downrank you. The reorder point is the earliest moment you can place an order and still have stock when the shipment arrives.
Expert tips
- Recalculate whenever sales velocity shifts by more than about 25%.
- Add extra safety stock for imported or single-supplier products — delays are longer and less predictable.
- If cash is tight, order smaller quantities more often rather than skipping the reorder point.
- Track your actual lead times for a few orders; most suppliers are slower than their quoted estimate.
How to interpret your results
- Dollar values are shown per sale, per order, or per item unless a result is explicitly labelled monthly, weekly, or daily.
- Percentages (margin, ROI, conversion rate) are easier to compare across products and price points than raw dollars — use them when you benchmark.
- A positive result means you're ahead after the costs and fees you entered. A negative result means the current numbers don't work — change a lever (raise price, cut a cost, lower ad spend) and recalculate.
- Treat the output as a planning estimate, not a guarantee. Fees, taxes, and conversion rates shift over time — re-run the numbers whenever a key input changes.
Common mistakes
- Reordering only when you're already out.
- Skipping safety stock — one busy weekend can burn through the buffer.
- Using a lead time that assumes 'best case' from the supplier.
Related Guides
Go deeper with plain-English guides on the same topic.
What Is a Good Profit Margin?
What counts as a healthy profit margin — and how it changes depending on what you sell and where.
Read guide →What Is A Good Profit Margin? Complete Small Business Profit Margin Guide
A 2026 profit margin guide — gross vs net vs contribution, what counts as a good margin, healthy benchmarks by industry and platform, formulas, and improvement strategies.
Read guide →Pricing Psychology Explained: 25 Strategies That Increase Sales
A 2026 pricing psychology guide — what it is, why it works, 25 specific techniques with examples, platform-specific applications, before/after scenarios, and ethics.
Read guide →How to Price Handmade Products
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FAQ
- How much safety stock?
- A common rule is 20–30% of expected lead-time sales, higher for seasonal or import-dependent items.
- What if daily sales fluctuate?
- Use a rolling 30-day average, and increase safety stock for high-variance products.
- What numbers do I need?
- Units in stock right now, average units sold per day, your supplier's realistic lead time in days, and a safety-stock buffer.
- Should I reorder now or wait?
- Reorder as soon as your stock reaches the reorder point. Above it, you can wait; at or below it, waiting risks running out before the shipment lands.
- Where do I find my lead time?
- Use the longest recent turnaround from your supplier, including production and transit — not the best case they quote.
- Why do stockouts matter so much?
- Listings lose ranking, ads waste spend, and repeat buyers go elsewhere. Recovering that momentum usually costs more than holding a little extra stock.
Why trust this calculator?
This tool uses standard mathematical formulas and commonly accepted calculation methods, shown openly in the Formula section above so you can verify the math yourself. Results are estimates based on the information you enter and do not account for every individual circumstance. For important financial, tax, legal, medical, or business decisions, please double-check with a qualified professional before acting on the numbers.
What to calculate next
Use this when you need to decide whether to reorder now or wait. Next, confirm the reorder point in detail, check how quickly the stock is actually moving, and price the cash risk of the next purchase.
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