Calculate SimplyHow to use
Start with the worked example to understand the inputs, then replace every relevant value with your own figures. Use one currency and consistent units throughout. Add or remove rows where offered; irrelevant conditional fields are disabled and excluded. Select Calculate after editing. Review negative values and any “not determined” result rather than assuming every scenario must be profitable. Download a text summary or print the page for your records.
Formula and assumptions
Enter current marketplace storage rates and aged tiers; no official live fee defaults are supplied. Base storage uses packaged unit volume and average opening/closing units, assuming linear monthly sales. Aged fees use the selected monthly assessment day, approximate units remaining then, and the latest applicable user tier. Each tier takes the greater of volume surcharge and per-unit minimum. The model groups inventory into one same-age cohort with no receipts or removals. It is a planning approximation, not an Amazon invoice calculator: actual inventory age distribution, exemptions, daily balances and marketplace rules may differ. Compare fees with remaining product contribution before deciding to liquidate.
volume ft³ = in³ / 1728; base storage = average units × unit volume × seasonal rate; aged fee = assessment-day units × max(unit volume × tier rate, minimum per unit)
Worked example
Example only: replace rates with your own figures.
Inputs
- Product dimension unit: in
- Packaged product length: 10
- Packaged product width: 6
- Packaged product height: 4
- Opening inventory units: 100
- Units sold per month: 10
- Inventory age on start date: 180
- Projection start month: 2026-10
- Projection months: 12
- Base storage rate Jan–Sep per ft³/month: 0
- Base storage rate Oct–Dec per ft³/month: 0
- Contribution profit per unit before storage: 10
- Monthly aged-fee assessment day: 15
| Aged tier begins at this many days | Aged surcharge per ft³/month | Minimum aged surcharge per unit/month |
|---|---|---|
| 181 | 0 | 0 |
- Unit storage volume: 0.138889 ft³
- Total projected storage cost: 0 USD
- Initial contribution before storage: 1000 USD
- Storage erosion of initial contribution: 0 %
- Remaining inventory units: 0
Frequently asked questions
Are the example rates current market prices?
No. Example inputs demonstrate arithmetic, not live prices, tax rules, salary surveys or sponsor benchmarks. Enter a dated quote, bill, manufacturer specification or verified fee schedule that applies to your situation. Compare a conservative and an optimistic scenario separately.
Why is a result not determined?
Some calculations have no meaningful value when a denominator is zero, savings are non-positive, a target cannot be reached or your data do not bracket an intersection. The tool leaves that result undetermined instead of displaying infinity or inventing a recommendation. Check the method and your inputs.
Sources
Sources explain the underlying concepts, not an endorsement of this website or its results. Method review: 20 October 2026.