Pre-premium amount if included
-Fair Market Value
Buyer's Premium Confirmation Tool
Confirm whether a price can already include a buyer's premium based on the auction bid increment, or calculate the added premium if it does not.
Enter an amount, percentage, and bid increment
The calculator will test the included-premium relationship and show the add-on math.
Premium already inside price
-Premium to add if not included
-Total if premium is added
-Buyer's premium confirmation tool for auction sales
AuctionMath's buyer's premium confirmation tool helps auctioneers, appraisers, bidders, dealers, and estate professionals review auction sale prices, hammer prices, bid increments, and premium percentages. Use it to test whether a reported sale price can mathematically include buyer's premium, estimate the premium added to a hammer price, support fair market value research, compare auction results, review invoices, and document pricing assumptions for appraisal or resale analysis.
How the included-premium check works
If the entered amount is a total that includes a premium, the calculator divides it by 1 plus the premium rate to estimate the hammer price before premium. It rounds that amount to cents and checks whether it is an exact multiple of the bid increment you entered. For example, $12 with a 20% premium backs out to a $10 hammer price and $2 premium; with a $5 increment, that is consistent with a premium-included total. The result is a mathematical possibility, not proof of how the auction reported its prices.
Interpret ambiguous results carefully
A number may be both a valid hammer bid and a plausible premium-included total. In that case, the calculator reports that it could be either. Confirm the price convention, premium basis, rounding, and bid increments against the original auction listing or invoice; third-party marketplaces may report totals differently.