Know exactly when to reorder every SKU
Try it right here — this is the real calculator, prefilled with example numbers. Swap in yours and the date updates instantly.
- Days you have left to order
- 2 days
- Projected stockout date (if you never reorder)
- Mon, Aug 31, 2026
- Total runway at current sales speed
- 30 days
Runs entirely in your browser — nothing you type is sent anywhere.
Want this for every SKU, without the tab-juggling?
The bulk forecaster is in development — one CSV upload will return this date for your whole catalog, plus an email before each one comes due. Join the waitlist and the first 50 members lock founding pricing at $19/mo.
Stockouts bleed rankings; overstock buries cash. The arithmetic is not the hard part — it is one formula, and a spreadsheet can hold it. The hard part is running it for all 200 SKUs, every week, and noticing the one that just went critical. ShelfOwl does the noticing.
Free forever for single-SKU math: no store connection, no plugin, no signup — results compute in your browser and every formula is published.
The spreadsheet tells you what you sold. It doesn’t tell you when to reorder.
Reorders run on gut feel
“Looks low, better order” is how stockouts and overstock both happen. The formula is not the obstacle — running it every week, for every SKU, is.
Margins are guesses
Fees, ads, returns and packaging hide between the supplier invoice and the payout. Sellers routinely overestimate margin — and then reorder the wrong SKUs. True COGS comes first; restock timing second.
Existing tools miss the middle
Enterprise inventory planners want a sales call and a four-week onboarding. Plugin tools lock you into one platform’s ecosystem. The middle — self-serve, CSV-in, answer-out — is where ShelfOwl sits.
This is what a restock forecast looks like
Waitlist open — not yet buyableExample data, showing the format the bulk forecaster will return. One CSV of sales, stock and lead times goes in; this comes back — every SKU’s remaining runway and the last safe day to place its purchase order, riskiest first. The two amber entries are the whole point: they are the orders you would have discovered too late. Look at the hoop earrings — 27 days of runway sounds relaxed until a 35-day supplier lead time turns it into an order that is already overdue. Runway alone is a comfortable lie; runway minus lead time is the truth.
- Linen shirt — navy / MAug 1146d runway
5.2/day · 240 on hand · 28d lead time
- Candle — cedar 8ozAug 1536d runway
11.4/day · 420 on hand · 14d lead time
- Ethiopia beans 12ozJul 18 — order now14d runway
8.8/day · 130 on hand · 21d lead time
- Hoop earrings — goldJul 16 — order now27d runway
2.1/day · 58 on hand · 35d lead time
- Whey vanilla 2lbAug 1758d runway
6.5/day · 380 on hand · 30d lead time
The math behind each row is the same published formula as the free calculator above. The bulk version that runs it across your whole catalog is still in development, gated on real demand signals rather than a roadmap fantasy — which is why this page offers a waitlist instead of a checkout. Planned pricing is $29/mo with a 14-day trial and no card. See the plan
Free calculators that answer real restock questions
Each tool is a full worked answer: the calculator, the formula spelled out, a worked example and an FAQ. Use them in any order — they chain together into a restock forecasting workflow.
- True COGS CalculatorCalculate your true COGS per unit — landed cost, marketplace fees, payment fees, ad spend, returns and packaging — and see your real gross margin per order.
- Reorder Point CalculatorWork out the exact inventory level that should trigger your next purchase order: daily sales × supplier lead time + safety stock. Free reorder point calculator, no signup.
- Safety Stock CalculatorCalculate how many buffer units protect you from demand spikes and late suppliers, using the max-sales × max-lead-time method. Free safety stock calculator, no signup.
- Latest Order Date CalculatorThe last calendar day you can place a PO before this SKU stocks out. One formula, one date — the calculation your spreadsheet can do but nobody remembers to run.
- Etsy Profit CalculatorSee your real profit per Etsy order after transaction, listing, payment processing and Offsite Ads fees — 2026 rates with sources.
- Inventory Turnover CalculatorInventory turnover ratio and days of inventory on hand from your annual COGS and average inventory value. See if your cash is moving or parked on shelves.
How restock forecasting works — four numbers, one date
No machine learning, no black box. Four calculations chained together, each one a free calculator on this site. Here they are in full — the same arithmetic the code runs, covered by automated test fixtures so the published formula and the shipped behaviour cannot drift apart.
- 1
Sales velocity
daily sales = units sold ÷ days in window
Use a 30–90 day window and exclude out-of-stock days, or the number lies to you.
- 2
Safety stock
safety stock = (max daily × max lead time) − (avg daily × avg lead time)
Buffer sized to survive your worst observed demand meeting your worst observed supplier delay. Run it
- 3
Reorder point
reorder point = daily sales × lead time + safety stock
The stock level that should fire a purchase order. Run it
- 4
Latest order date
latest order date = today + (stock − safety stock) ÷ daily sales − lead time
The answer in the hero, and the one number the other three exist to produce. Run it
Every formula on the site is documented the same way on the methodology page, including the judgment calls and the known limits.
Every formula is public
verifiableThe exact arithmetic behind every calculator is written out on the methodology page. If you disagree with a formula, you can see precisely what to disagree with.
Fee rates carry receipts
checked 2026-07-28Prefilled marketplace rates link to the official pricing page they came from, with the date we verified them — all on the sources page, changes logged on rate updates. Anything we could not verify against an official page is labelled as such, in the calculator itself.
Your data stays yours
0 requestsFree calculators run entirely in your browser — open your network tab and watch nothing happen. No store OAuth. The only thing we store is an email address, and only if you choose to join the waitlist.
Built to be checked, not believed
Made for the brands spreadsheets were failing
SMB ecommerce operators with tens to a few hundred SKUs and no ERP — the exact zone where restock forecasting matters most and tooling is thinnest. If your inventory truth lives in a spreadsheet and reorders get decided by scrolling it, this was built for you.
- Apparel brandsjuggling size and colour variants against seasonal buys — Forecasting guide
- Coffee roasterstiming green-bean orders around a roast schedule — Restock alerts guide
- Handmade & jewellery sellersbalancing materials against made-to-order queues — Order management guide
- Marketplace sellerson Etsy, Amazon or TikTok Shop who need fee-true margins — Start with fees
Why not an inventory platform or a store plugin?
To get started
- ShelfOwl
- Open a page — nothing to install
- Enterprise planner
- Sales call, then weeks of onboarding
- Store plugin
- Install into one store
Where inventory lives
- ShelfOwl
- Anywhere a CSV can come from
- Enterprise planner
- Multi-warehouse, any channel
- Store plugin
- The one store it plugs into
Pricing
- ShelfOwl
- Free single-SKU · $29/mo planned for bulk
- Enterprise planner
- Request a quote
- Store plugin
- Per-store subscription
Shows its arithmetic
- ShelfOwl
- Every formula published
- Enterprise planner
- No
- Store plugin
- No
None of that makes the platforms wrong — at multi-warehouse scale they are the right tool. It makes them the wrong shape for a spreadsheet-run catalogue that needs an answer this afternoon.
Start free today. The bulk version is still being built.
Run any calculator free, forever — no account, no usage cap, no email wall, and nothing you type ever leaves your browser. The bulk forecaster for people juggling more SKUs than browser tabs is not built yet: it will be $29/mo (or $290/yr) with a 14-day trial and no card, and the first 50 waitlist members will lock founding pricing at $19/mo. Joining the waitlist costs nothing, commits you to nothing, and tells us which parts to build first.
Or see what’s in the paid plan.