Profit Hawk
Free tool · For Amazon FBA sellers

Reorder Point Calculator
for Amazon FBA sellers.

Find the exact on-hand + on-order level that should trigger your next PO — so new stock arrives before you run out, without tying up cash you don't need to.

?
What question does this answer
“At what inventory level should I place my next PO so I don't run out while waiting on the new shipment?”
1

Calculate your reorder point

Enter your SKU's sales data. We'll do the math.

units
units
Don't know your σ?

Take 60–90 days of daily sales (excluding stockout days) and run STDEV.P in Google Sheets. If sales are pretty stable, a quick approximation is roughly 30–40% of your average daily sales.

days
Service levelhow often you want to NOT stock out
Your reorder point
989units

What this meansPlain English

Place your next PO when your available + inbound inventory drops to about 989 units. At a 95% service level, that protects you from stocking out in 95% of lead-time cycles.

Where it comes fromBreakdown

900 units of expected lead-time demand (avg sales × lead time) + 89 units of safety stock (Z × σ × √L) = 989 units.

Lead-time demand
900units
Safety stock buffer
89units
Z-score (95%)
1.65
Stockout risk / cycle
5%
2

When should I place the order?

Plug in your current available inventory and we'll tell you what to do today.

units

On-hand units plus units already on order (in transit, at the freight forwarder, or at Amazon waiting to be received).

Recommended action
Reorder now
Your reorder point
989 units
Current available inventory
750 units
Status
You are already 239 units below your reorder point.
Estimated stockout date
—
Expected stockout length
~8 days

Even if you place the PO today, the new shipment won't arrive before current inventory runs out.

How it works

The formula, in plain English.

You don't need a stats degree. Reorder point answers one question: how low should my inventory drop before I fire the next PO, given how fast I sell and how long my supplier takes?

Reorder Point =Avg sales × Lead time+Safety stock
d̄ · L
Expected lead-time demand. Average daily sales × supplier lead time — what you'll sell while waiting for the new shipment. See lead-time demand for the full definition.
Z · σ · √L
Safety stock buffer. The cushion that absorbs demand variability. Z = your service level, σ = how spiky daily sales are, √L = how long the buffer has to last. This is your safety stock.
ROP
Reorder Point. Add the two together. Hit this number? Fire the next PO. See the reorder point glossary entry for the deeper rationale.

Worked example

A steady seller on Amazon US with a moderately reliable supplier.

Average daily sales20 units
Std. dev. of daily sales (σ)8 units
Lead time (L)45 days
Service level (A Products)95% · Z = 1.65
Lead-time demand20 × 45 = 900
Safety stock1.65 × 8 × √45 ≈ 89
Reorder point
989 units
Watch out for

Common reorder-point mistakes.

Most stockouts (and most overstocks) aren't a math problem — they're an assumption problem. Here are the ones we see most often inside Amazon catalogs.

01

Trusting your supplier's average lead time

“30 days” often means 22 on a good run and 45 when something slips. Plan for the realistic worst case, not the brochure number.

Fix: Add lead-time variability into σ, or use the upper bound (e.g. P90) of your last 6 POs.
02

Treating every SKU the same

A slow, lumpy seller and a stable hero SKU need very different buffers. One blanket service level wastes cash on one and risks stockouts on the other.

Fix: Set service levels by SKU tier — A items high, C items lower.
03

Ignoring seasonality & promo spikes

Q4, Prime Day, Mother's Day — historical averages will under-buffer you going in and over-buffer you on the way out.

Fix: Recalculate σ on a rolling window, and add a seasonality multiplier on known peaks.
04

Setting it once and forgetting it

Sales velocity, lead times, and demand variability all drift. A buffer set in January is rarely the right one in June.

Fix: Recalculate at least monthly — or automatically on every PO decision.
05

Triggering off on-hand only

If you don't include units already in transit, you'll double-order while a PO is on the way and over-stock yourself.

Fix: Compare reorder point to on-hand + on-order, every time.
06

Counting only FBA inventory

If you also hold units in AWD, a 3PL, or inbound shipments, your real available cover is higher than what FBA shows.

Fix: Calculate on FBA + AWD + 3PL + inbound — not FBA on hand alone.
When this calculator isn't enough

Great for one SKU.
Tricky for a full catalog.

This tool is perfect for sanity-checking a single SKU. But running reorder points manually across an Amazon catalog falls down fast — because real catalogs aren't static.

  • Seasonal demandDemand variability (σ) shifts throughout the year — your Q4 and Q1 numbers behave like different products entirely.
  • Prime Day & promo spikesOne-off events distort your rolling average if they aren't separated out from baseline demand.
  • Multiple marketplacesUS, CA, UK, and EU each have their own velocity and lead time — a single formula won't fit them all.
  • FBA, AWD & 3PL togetherYour true cover depends on every warehouse plus inbound — not just what FBA shows on hand.
  • Supplier lead time changesWhen your supplier slips by a week, your formula needs to slip with it — automatically, not next quarter.
  • Recalculating across hundreds of SKUsManual math doesn't scale. Every PO decision means re-running the formula for every SKU it touches.
▲ Profit Hawk

Track reorder points automatically across every SKU.

Profit Hawk connects to your Amazon Seller Central and recomputes reorder points, safety stock, and days of cover continuously — using your real sales, real lead times, and your live FBA + AWD + 3PL inventory.

  • Per-SKU service levels by ABC tier
  • Seasonality & promo-aware demand modeling
  • Multi-marketplace, multi-warehouse view
  • PO alerts before you cross reorder point
Start free trialSee Profit Hawk →
FAQ

Reorder points, answered.

The questions Amazon sellers actually ask us — about service levels, lead-time variance, seasonality, and what to do when your data is messy.

How is safety stock different from a reorder point?
Safety stock is the cushion you keep in addition to expected demand during lead time. Reorder point is the inventory level at which you actually place your next PO. ROP = (avg daily sales × lead time) + safety stock. You hit ROP first; if everything goes to plan, you never dip into safety stock.
Should I trigger on on-hand only, or on-hand + on-order?
On-hand + on-order. If you only look at on-hand, you'll keep ordering after you've already placed a PO that's in transit and double-up your inventory. Always include units that are on the water but not yet received in your trigger calculation.
What service level should I use?
Match the tier to how critical the SKU is. A Products (95%) for hero SKUs where stockouts crush ranking and velocity. B Products (90%) for the balanced middle. C Products (85%) for slow-moving long-tail items where holding extra inventory ties up cash you'd rather deploy elsewhere.
What if I don't know my standard deviation?
Take 60–90 days of daily unit sales (excluding stockout days) and run STDEV.P in Google Sheets — that's your σ. If you don't have clean data, a working estimate is roughly 30–40% of your average daily sales for typical FBA products with moderate variability.
What if my lead time isn't consistent?
Use your worst-case realistic lead time instead of the average. The classic reorder-point formula assumes fixed lead time and only models demand variability. Plugging in the slow end of your lead-time range is the simplest way to absorb that variance without moving to a more complex formula.
Should I use the same reorder point for every SKU?
No. Different SKUs have different demand patterns, lead times, margins, and strategic value. Tier your catalog (A/B/C) and apply different service levels to each tier. One global setting almost always under-protects your top items and over-stocks your tail.
How often should I recompute the reorder point?
Monthly at minimum, and immediately whenever your supplier, freight forwarder, or sales velocity changes. Seasonal SKUs need a recalc going into each season. The cost of going dark on Amazon is high enough that yesterday's reorder point can be today's stockout.
Can a reorder point prevent all stockouts?
No buffer makes stockouts impossible — that's why it's tied to a service level, not 100%. The reorder point is a statistical cushion, not a guarantee. Black-swan events (supplier failures, viral demand) still need playbooks beyond the formula.
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▲ Profit Hawk

Want this tracked automatically across all your Amazon SKUs?

Profit Hawk recalculates reorder points, safety stock, and days of cover using your real Amazon inventory and sales data — across every SKU and every marketplace.

Start free trialSee Profit Hawk