✓ 12 Marketplaces · Aged Fee Timeline 100% Free · No Sign-up Built for 2026 Rate Cards

Amazon Inventory Health Simulator

Watch your monthly storage and aged inventory surcharges pile up day by day across 12 Amazon marketplaces. Get a restock quantity and reorder window, then see what happens if sales drop by half.

12-Month Fees
—
storage + aged surcharge
Aged Surcharge (12-mo)
—
starts at day 181
Days of Cover
—
at current pace, no restock
Aged Fee Starts
—
on your current stock
Sales −50% Impact
—
extra fees over 12 months
⚙ Your Numbers edit any field
Marketplace
Rates shown in local currency, published by Amazon
Size Tier
Off-peak (Jan–Sep) / peak (Oct–Dec) monthly rates
Unit Dimensions ?—
L
W
H
Packaged dimensions in inches
Current Inventory ?
units
Current Stock Age ?
days
Days since these units arrived at Amazon
Monthly Sales
units
Restock Lead Time ?
days
Restock Every
days
How often you place a replenishment order
Safety Buffer
days
Extra days of cover to absorb delays
📊 Breakdown your numbers, live
🎯 Restock Plan based on your sales pace
Reorder Point
—
order when inventory hits this level
Reorder By
—
days from today
Restock Quantity
—
covers one cycle
Reorder point = daily sales × (lead time + safety). Restock quantity = daily sales × cycle — each purchase order covers one replenishment cycle, while the reorder point bridges the lead-time gap.
⚡ Stress Test
💰 Cumulative Storage Fees next 12 months, day by day
Purple is the regular monthly storage fee. Red is the aged inventory surcharge — it starts small and jumps sharply the moment stock crosses the 271-day mark (181 days in the US and Canada). The orange markers show where your current stock hits those ages.
📦 Inventory Level sawtooth of sales and restocks
The dashed orange line is your reorder point. Purple dots are restock arrivals. Under the stress test the sawtooth stops draining — that plateau is exactly what turns into aged surcharge fees.
How the math works
Unit volumeL × W × H → cubic feet (US: inches ÷ 1,728) or cubic metres (cm ÷ 1,000,000; UK: cm ÷ 28,316.8 = cu ft)
Daily sales paceMonthly sales ÷ 30.4
Monthly storage feeUnits × volume × rate — Jan–Sep off-peak, Oct–Dec peak, per marketplace and size tier (rates embedded per market)
Aged surchargeSnapshot on the 15th of each month, per unit of volume by age. US & CA start at 181 days; UK & EU start at 241 days; JP starts at 271 days. The 271–300 day tier is several times the 241–270 tier in every marketplace.
Reorder pointDaily pace × (lead time + safety buffer)
Restock quantityDaily pace × cycle — each PO covers one replenishment cycle; the reorder point bridges the lead-time gap
AssumptionsFIFO depletion (oldest units sell first), restocks arrive on schedule, fees accrue daily, surcharge snapshots monthly on the 15th. Excludes the storage utilization surcharge. The pre-271-day tiers don't apply to Clothing, Shoes, Bags, Jewelry & Watches in most marketplaces.