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Auction total-cost calculator

The hammer price is never the price you pay. Enter every amount in the currency of the sale. The tool adds the buyer's premium, sales tax and shipping to show the real total and the effective premium rate.

The price the auctioneer calls when the hammer falls.

The percent the house charges on the first slice of the hammer price. For a flat premium, enter it here and leave the tier fields as they are.

%

The hammer price where the first rate stops. Leave it at 100000000 for a flat premium.

The percent on the part of the hammer price above the first slice, up to the second limit.

%

The hammer price where the second rate stops. Leave it at 100000000 when there is no third slice.

The percent on the part of the hammer price above the second limit.

%

A flat amount added per lot, for example the fixed part of a platform's protection fee.

Most places tax the premium too; some tax only the hammer price. When in doubt, leave the default.

The rate where the lot is sold or delivered.

%

Packing, shipping and insurance the house quotes, or 0 when you collect.

How we calculated this

The tool does not convert currencies. Enter the hammer price, limits, fees and shipping in the currency of the sale, and every result is in that same currency.

A tiered buyer’s premium charges a different percent on each slice of the hammer price. Buyer’s premium = first slice × first rate + second slice × second rate + third slice × third rate, plus any fixed buyer fee.

Enter each slice limit as a hammer price, with the rate the house publishes for that slice. For a flat premium, set the first rate and leave the other fields as they are.

Example from Christie’s published schedule for London and New York: 28% up to £1.5M or $2M, 22% to £6M or $8M and 15% above. Enter 28, 2000000, 22, 8000000 and 15 for a sale in dollars.

Sales tax is applied to the hammer price, or to hammer price plus premium, depending on the tax base you choose.

Total = hammer price + buyer’s premium + sales tax + shipping. Effective premium rate = (total − hammer price) ÷ hammer price × 100.

Published premium schedules cited on this site: Christie's buyer's premium (christies.com/en/help/buying-guide-important-information/financial-information), Heritage terms and conditions (ha.com/c/ref/terms-and-conditions.zx), Sotheby's premium help page (help.sothebys.com) and Catawiki's Buyer Protection fee (catawiki.com/en/help/fees/what-is-the-buyer-protection-fee).

Premium ranges in the summary come from the buyer_premium_pct values on the listings, which hold each house's first-slice rate; a figure appears only where the house publishes one.

Method checked on 2026-10-21.

Planning figures only, not financial or legal advice. Rates, tiers, taxes and fees change; read the house's own terms before you bid. Beware of auction fraud and shill bidding — never wire money or pay by gift card to a seller you cannot verify.

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