Profit Hawk
Free tool · For Amazon FBA sellers

Promotion Inventory Planner
for Amazon FBA.

Plan how much inventory you need before Prime Day, a coupon, a Lightning Deal, or a seasonal push — without running out mid-event or sitting on a mountain of stock after.

?
What question does this answer
“How much inventory do I need before a Prime Day, coupon, deal, ad push, or seasonal promotion?”
1

Size your promo inventory

Baseline sales, expected lift, promo length, and what you have on the way.

units
Expected promo liftpick a preset or type below
%
days
units
units
days
days
Extra units needed
700units

What this meansPlain English

Shortfall of 700 units, and your reorder lead time (60 days) is longer than the promo window (2 days). Cut deal depth, throttle ads on this SKU, or pull a smaller promo before you burn through everything.

Where it comes fromBreakdown

Promo daily run rate
~150 units / day
Expected promo units
300 units
Post-promo halo units
700 units
Inventory needed
1,000 units
Available + inbound
300 units
Ending inventory
-700 units
Stockout risk

Available + inbound doesn't cover expected demand. Top up via air freight if lead time allows, otherwise reduce deal depth or throttle ads on this SKU before the window opens.

How it works

Lifted demand × promo days, plus halo.

A promo is a temporary multiplier on your baseline run rate. The math isn't fancy — getting the inputs honest is what matters. Don't overpromise rank modeling; handle promos separately from baseline demand.

Promo Demand =Baseline × (1 + lift%)×promo days
d̄
Baseline daily sales. Your clean, pre-promo run rate. Strip out earlier promo days so you don't compound demand variability from prior events.
L%
Expected lift. Conservative for a first event, calibrated against your last comparable promo for repeat events.
P
Promo length in days. Calendar days the deal is live. Lightning Deals are hours; coupons can run open-ended.
H
Post-promo halo. A smaller lift over a short window after the event from BSR carryover.
I
Inventory needed. Promo demand + halo demand — the total units that should be checked in at FBA before the window opens.

Worked example

A hero SKU running a 2-day Prime Day Lightning Deal with a 7-day post-event halo.

Baseline daily sales50 units
Lift+300%
Promo run rate200 units / day
Promo length2 days
Promo demand200 × 2 = 400 units
Halo (+150% × 7 days)125 × 7 ≈ 875 units
Inventory needed1,275 units
Plan against
1,275 units
Watch out for

Common promo planning mistakes.

Stockouts during a promo are the most expensive inventory mistake an Amazon seller can make — they hit BSR, ad ROAS, and the entire reason you ran the event.

01

Using promo demand in your baseline forecast

A Prime Day or Lightning Deal will inflate your trailing 30 / 60 / 90-day rolling averages for weeks. Replenishment plans built on that data over-order long after the event is over.

Fix: Strip promo days from baseline forecasting and add promo demand back as a separate, named event.
02

Forgetting the BSR halo

Bestseller rank lifts after a successful promo, which keeps demand 30–80% above baseline for a few days to a couple of weeks. Plan without it and you'll stock out right after winning.

Fix: Add a post-promo elevated demand window with a smaller lift.
03

Cutting it tight to look 'efficient'

Running out mid-deal isn't an efficiency win — it kills BSR, ad ROAS, and the entire reason you ran the promo. Inventory is the cheapest variable here.

Fix: Plan for the upper end of your lift estimate, not the average.
04

Forgetting FBA receiving timelines

Units delivered 3 days before Prime Day may still be checking in when the event starts. Lightning Deals require checked-in inventory by the lock-in date — not just delivered.

Fix: Have promo inventory checked in 7–10 days before the event, not delivered.
05

Ignoring inbound-on-the-water units

If your math only counts FBA on-hand, you'll over-order and end up with a sit-still mountain post-event.

Fix: Always include FBA + AWD + 3PL + inbound that lands before the promo window.
06

Treating every variation the same

Aggregating velocity at the parent ASIN level under-stocks the popular child and over-stocks the rest. Promo lift is rarely even across a parent.

Fix: Plan per ASIN, not per parent — especially for high-velocity hero children.
When this calculator isn't enough

One SKU is easy.
A full Prime Day plan is not.

This calculator is great for sanity-checking one promo. Running an actual event across a catalog requires history-aware lift modeling, multi-warehouse reservation, and the discipline to keep promo demand out of your baseline forecast.

  • Lift forecasting from historyPicking a lift % manually is a guess. Modeling it from your own past promos, by deal type and category, is a different game.
  • Separating promo from baseline automaticallyStripping promo days from rolling averages is fiddly in spreadsheets. Missing one of them quietly skews months of replenishment.
  • Reservation across FBA, AWD & 3PLKnowing where the units sit and when they'll be ready to sell at Amazon is the hard part of promo planning — not the math.
  • Halo demand modelingBSR halos are real but vary by SKU. A flat post-promo lift in a calculator is a starting point, not a plan.
  • Catalog-wide event planningPrime Day isn't one SKU. Running this math 80 times in a spreadsheet right before lock-in is how mistakes happen.
  • Mid-event throttlingWhen demand spikes higher than planned, knowing when to pull back ad spend or deal depth in real time is what saves the SKU.
▲ Profit Hawk

Plan every promo without contaminating your baseline.

Profit Hawk tags promo days, models lift from your own history, reserves inventory across FBA, AWD, and 3PL, and keeps your baseline replenishment math clean before, during, and after every event.

  • Promo-aware demand forecasting
  • Seasonality & halo modeling per SKU
  • FBA + AWD + 3PL inventory visibility
  • Automated replenishment planning
Start free trialSee Profit Hawk →
FAQ

Promo planning, answered.

Practical questions sellers ask before Prime Day, Q4 deals, and bigger seasonal pushes.

How much lift should I expect from Prime Day?
It depends on category, deal type, and how well-ranked your SKU is — but typical ranges are +100–300% for a Lightning Deal, +200–500% for a Best Deal, and +300–800% for a hero SKU running coordinated PPC + display + email. Be conservative on your first event for a given SKU and trust your second event's actual numbers more than any forecast.
Should I include the promotion in my baseline demand forecast?
No. That's one of the most damaging mistakes in FBA forecasting. A Prime Day or Lightning Deal is a one-off event that distorts a rolling average for weeks or months afterwards. Always separate promo demand from baseline and add it back as a discrete event with its own units, ad spend, and lift assumption.
What about the post-promo demand bump?
Real, but smaller and shorter than most sellers assume. A successful event lifts BSR, which can carry 30–80% above baseline for 3–14 days before reverting. Build a halo line into your plan, but don't size inventory as if the lift is permanent.
What's the difference between a coupon, a Lightning Deal, and Prime Day?
Coupons (5–20% off) usually add a small but durable lift, often without a clear start/end. Lightning Deals run 4–6 hours and concentrate demand into a tiny window — they need different inventory math than a longer event. Prime Day is an arrival event for the marketplace as a whole, so even SKUs without a deal often see lift from category traffic.
How early should I have inventory in FBA before the promo?
Have the full promo inventory checked in at FBA at least 7–10 days before the event starts. FBA receiving routinely slips, and lightning deals require units to be active well before the lock-in date. The day-of scramble is the most expensive way to ship a promo.
What if my reorder lead time is longer than the promo window?
Then ocean replenishment can't save you mid-event — air freight is your only real option, and even that needs to be moving days before you confirm the deal. The cleanest answer is to either (a) cut deal depth to slow burn, (b) throttle PPC spend on the SKU, or (c) pull a smaller event you can actually stock for.
Should I also plan extra units for Amazon variation children?
Yes, separately. Each variation has its own velocity and lift profile. Aggregate planning at the parent level under-stocks the popular child and over-stocks the rest. Run this calculator per ASIN.
Does this account for ad spend changes during the promo?
Indirectly — the lift % you enter should already reflect both the deal mechanic and the ad spend you plan to run alongside. If you're doubling ad budget, your lift estimate should be higher. Run the calculator at the most realistic combined scenario, not the deal-only one.
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▲ Profit Hawk

Want this tracked automatically across every promo?

Profit Hawk separates promo demand from baseline, models lift from your own history, and keeps replenishment planning honest before, during, and after every event.

Start free trialSee Profit Hawk