Amazon BSR to Sales Calculator
Calibrated against your own known sales.
This calibrates a power-law curve against your own known sales, which is more reliable than a generic estimator — but only within your own category, and only while the curve holds.
Competitor units per month
618
2.8× your volume
Calibrating against your own sales is far more reliable than a generic estimator, because the category's decay curve cancels out of the ratio. It still assumes both products sit on the same curve — which breaks down when one is heavily advertised and the other is not.
How the Amazon BSR to Sales Calculator works
The most reliable way to estimate a competitor's volume is to calibrate against your own. Because both products sit on the same category curve, the curve cancels out of the ratio — leaving an estimate that does not depend on anybody's proprietary data.
Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price — check the platform's current fee schedule before you price a product against it. This is not tax or business advice.
Frequently asked questions
How does calibrating against my own sales help?
The unknown category constant appears in both estimates and divides out. You are left with a ratio of ranks raised to a decay exponent, which is far more robust than an absolute estimate.
What is the decay exponent?
How steeply sales fall as rank worsens. Around 0.8 is a common starting point, but it varies by category — fit it by checking the ratio against a product whose sales you can verify.
What breaks the assumption?
One product being heavily advertised and the other not, seasonality affecting them differently, or a recent price change that has not yet worked through the rank. The curve assumes both products are in a comparable state.
How volatile is BSR?
Very. It updates hourly and reflects recent velocity, so a single good day moves it sharply. Use a thirty-day average rather than a snapshot for anything you intend to act on.