Profit Hawk
Free tool · For Amazon FBA sellers

Inventory Turnover& GMROI
Calculator.

See how fast your inventory turns, how many days of stock you're holding, and how many gross-margin dollars each $1 of inventory cost actually generates.

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What question does this answer
“Is my inventory turning fast enough, and is it generating enough gross margin for the cash it uses?”
1

Enter your inventory & profit numbers

Period defaults to annualized — switch if you're looking at a quarter or half-year.

Period lengthresults annualize for comparison
COGS over the periodenter directly or compute it
$
$
$
Gross profit input% margin or $ profit
%

Gross profit used: $400,000 · margin 40.0%

Inventory turnover
6.0turns / yr
Days of inventory
61days
GMROI
$4.00per $1

What this meansPlain English

~6.0 turns / year is a healthy range for FBA. Aim to push GMROI up by either widening margins or reducing average inventory — not by chasing turnover at the expense of margin.

Turnover improvement kit

Turn your 6.0x turn rate into a cash-efficiency plan

Get a practical kit for ranking SKU turn rates, spotting slow-moving inventory, and tying inventory efficiency back to gross margin.

  • PDF of this calc — 6.0x turn · $600,000 COGS · $100,000 avg inventoryInstant
  • Multi-SKU template — for ranking turn rate by productSheet
  • Extended calculator — by-SKU turn rates + GMROI breakdownsTool
  • 5-day FBA playbook — inventory efficiency, one short email a dayCourse
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How it works

Three numbers that tell the truth about your inventory.

Turnover answers “how fast.” Days of inventory answers “for how long.” GMROI answers “for how much.” Use them together — any one alone is misleading.

Turnover =COGS÷Avg Inventory Value
T
Inventory turnover. How many times your average inventory cycles in the period. See inventory turnover for the full definition.
DOI
Days of inventory. Period days ÷ period turnover (so 365 ÷ annualized turnover for an annual view). The average number of days a unit sits before selling.
GMROI
Gross margin return on investment. Gross profit dollars ÷ average inventory cost. The cash-efficiency view — GMROI tells you how much gross profit each $1 of inventory generates.
GM%
Gross margin percentage. Gross profit ÷ revenue. The lever that moves GMROI alongside turnover.

Worked example

A mid-sized FBA brand looking at a full year.

Revenue (annual)$1,000,000
COGS$600,000
Gross profit$400,000 (40%)
Average inventory value$100,000
Turnover (COGS ÷ avg inv)600,000 ÷ 100,000 = 6×
Days of inventory (365 ÷ turnover)365 ÷ 6 ≈ 61 days
GMROI (GP ÷ avg inv)$400,000 ÷ $100,000 = $4
GMROI
$4 / $1

Every $1 of inventory cost generates $4 in gross profit per year — a healthy FBA number. Push harder by widening margin, not by stocking leaner.

Watch out for

Common turnover & GMROI mistakes.

A high turnover ratio is only good news if margin and service level held up. These are the patterns we see quietly destroy cash efficiency on Amazon catalogs.

01

Chasing high turnover by stocking too lean

Higher turnover looks better on paper, but if you're under-buffering you'll stock out — and on Amazon, stockouts cost rank, ad efficiency, and reorder velocity.

Fix: Pair turnover targets with a service level constraint. Don't optimize one without the other.
02

Chasing high turnover by cutting margins too hard

Promo-discounting your way to a higher turnover ratio shows up as a lower GMROI. You're moving units faster but earning less per dollar of inventory.

Fix: Watch GMROI alongside turnover. If turnover is up but GMROI is down, you're trading margin for velocity.
03

Using retail value for 'average inventory'

Inventory should be measured at landed cost, not list price. Mixing the two inflates turnover and makes GMROI meaningless.

Fix: Use cost-based inventory value across the period. Same currency, same denominator, every time.
04

Ignoring inbound and AWD dollars

Inbound inventory is already paid for and tying up cash. Leaving it out flatters your turnover and hides cash drag.

Fix: Include FBA + AWD + 3PL + inbound at cost in the average inventory value.
05

Comparing a 90-day number to an annual benchmark

A 1.5-turn quarter is not 'slow turnover'. Annualized, that's 6 turns — perfectly healthy. Sellers panic at quarterly snapshots all the time.

Fix: Annualize before benchmarking. The calculator does it for you.
06

Looking at the catalog total only

Aggregate turnover masks the SKUs that are killing you. The top quartile turns fast; the bottom quartile sits forever. The middle quartiles can do anything.

Fix: Run turnover by ABC tier and watch the slowest tier — that's where the cash trap lives.
When this calculator isn't enough

Catalog-level math hides
where the cash sits.

This calculator nails the headline numbers for one period. The actual lever is SKU-level — knowing which SKUs are slow movers, which are GMROI heroes, and which are quietly trading margin for velocity.

  • SKU-level turnover and GMROICatalog-level numbers hide the slow movers. Per-SKU turnover and GMROI are where the actual decisions live.
  • Rolling inventory snapshotsTrue average inventory is a rolling, time-weighted number — not a (beginning + ending) / 2 approximation.
  • FBA + AWD + 3PL + inbound visibilityAll four warehouses hold cash. A spreadsheet that only sees FBA understates inventory and overstates turnover.
  • Slow-mover liquidation playbooksKnowing a SKU is slow is step one. Routing it to removal, FBA Liquidations, or off-Amazon channels is what frees the cash.
  • Margin trend awarenessTurnover up + GMROI down means you're discounting your way to higher velocity. That's a slow leak that shows up in cash before it shows up in P&L.
  • Catalog-wide GMROI rankingKnowing your top-10 and bottom-10 SKUs by GMROI is how you decide where to deploy more cash and where to stop reordering.
▲ Profit Hawk

Track turnover & GMROI per SKU automatically.

Profit Hawk computes turnover, days of inventory, and GMROI per SKU continuously — using your real Amazon sales, your landed cost, and your live FBA + AWD + 3PL inventory. The slow movers and the GMROI heroes surface themselves.

  • Per-SKU turnover & GMROI ranking
  • Slow-mover liquidation alerts
  • FBA + AWD + 3PL inventory at cost
  • Margin trend & GMROI drift detection
Start free trialSee Profit Hawk →
FAQ

Turnover & GMROI, answered.

The practical questions FBA sellers ask before they trust the headline number.

What's a 'good' inventory turnover ratio for Amazon FBA?
Most healthy FBA businesses run between 4 and 12 turns per year. Below 4 turns / year means cash is sitting in slow stock and probably eating long-term storage fees. Above 12 turns / year is great if margin is intact and you're not bleeding stockouts — if you are, the high turnover is hiding a problem.
What is GMROI and how is it different from turnover?
GMROI (Gross Margin Return on Investment) = gross profit dollars / average inventory cost. Turnover tells you how many times your inventory cycles. GMROI tells you how much gross profit each $1 of inventory generates. A SKU can have high turnover and low GMROI (you're churning at razor-thin margin) or low turnover and high GMROI (premium, slow-moving, but cash-efficient). Both numbers together tell the real story.
Is chasing high inventory turnover always good?
No — and this is the most common mistake. Sellers who chase turnover by understocking hit stockouts, lose BSR, and inflate ad spend trying to recover. Sellers who chase turnover by cutting prices erode margin. The goal isn't max turnover — it's the highest sustainable GMROI without breaking your service level. Stocking too lean or cutting margins too aggressively to look 'efficient' usually loses money.
What counts as 'average inventory value'?
Average inventory at landed cost (not retail) across the period. Practically: (beginning inventory value + ending inventory value) / 2 for a quick approximation, or a true rolling average of weekly/monthly inventory cost snapshots if you can pull them. Include FBA + AWD + 3PL + inbound at cost.
Should I include inbound and AWD inventory?
Yes — if it's already paid for. The dollars are tied up regardless of which warehouse it sits in. Excluding inbound makes your turnover look better than it really is and hides cash drag.
What period length should I use?
Annualized (365 days) is the industry-standard comparison. Use shorter periods (90 or 180 days) when you want to see directional change inside the year — and let the calculator annualize the result for you. Don't compare a 90-day turnover number to an annual benchmark without annualizing first.
How is days of inventory different from days of cover?
Days of inventory is computed off your financials — period days ÷ period turnover (so 365 ÷ annualized turnover when you're looking at a full year). It's backward-looking. Days of cover is computed off your run-rate — current inventory ÷ recent daily sales — and is forward-looking. Both matter, but they answer different questions: 'how cash-efficient was I last quarter?' vs. 'will I stock out next week?'
How often should I recompute this?
Monthly for the catalog level, quarterly per ABC tier or per top SKU. Watch the directional change — a slowly declining turnover or a slowly declining GMROI is a leading indicator of inventory bloat or margin compression months before the cash-flow problem shows up.
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▲ Profit Hawk

Want this tracked automatically across every SKU?

Profit Hawk recalculates turnover, days of inventory, and GMROI continuously per SKU — using your real Amazon sales and live FBA, AWD, and 3PL inventory at cost.

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