Gemsmakers · Antique Dealer Tools
Antique Auction Buyer’s Premium and Total Cost Calculator
The hammer price is only one part of the cost of acquiring an antique at auction. This calculator separates the buyer’s premium from fixed buyer fees, estimated tax, and logistics, then reports the effective premium burden relative to the hammer price.
Calculator
Enter your figures below. Results update from the assumptions you supply; check your agreement, fee schedule, and local requirements before making a decision.
How to use this tool
- Enter the expected hammer price and choose a percentage or tiered premium structure. For tiers, provide threshold | rate lines; the selected tier rate applies to the full hammer price.
- Add buyer fees, applicable tax rate, shipping, insurance rate, and collection charges.
- Review the total landed cost and effective premium percentage. Confirm the auction house’s exact tax base and fee schedule before bidding.
Calculation method
Buyer premium = hammer × selected rate (or tier rate). Estimated tax = (hammer + premium + buyer fees) × tax rate. Insurance = hammer × entered insurance rate. Total acquisition cost = hammer + premium + buyer fees + tax + shipping + insurance + collection charge.
Worked example
At a 1,000 hammer price with a 20% premium and 8% tax applied to hammer plus premium, estimated tax is 96 before any other buyer fees. Shipping, insurance, and collection charges then increase the landed cost further.
Important assumptions and limitations
- Auction houses differ in their tax base, buyer-fee definitions, and whether premium is taxed. This tool uses the explicit basis shown in the formula.
- Insurance can be based on hammer price, declared value, or a separate carrier formula; here it is a percentage of the hammer price.
- Treat the final figure as a budgeting estimate until all written auction terms and shipping quotes are confirmed.
Frequently asked questions
What is a buyer’s premium?
It is the fee paid by the buyer to the auction house in addition to the hammer price.
What does effective premium percentage mean?
Here it is buyer premium plus fixed buyer fees divided by hammer price. Taxes and logistics are reported separately.
Why is tax calculated on hammer plus premium?
That is the assumption selected for this model. Some jurisdictions or auction houses use a different taxable base, so verify the invoice terms.
Does shipping count toward effective premium?
No. Shipping, insurance, tax, and collection charges are included in total landed cost but excluded from the premium-only percentage.
Can I compare auction houses?
Yes. Run the calculator with each house’s published premium and fee schedule, while keeping the same target lot and logistics assumptions.
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