What it does
The winning bid at an auction, the hammer price, is not what you pay. The auction house adds a buyer’s premium, there may be tax on it, and shipping comes on top. Sellers lose a commission and fees from the other end. This calculator shows both sides so there are no surprises.
On the buying side it gives the total you will pay and the highest bid that keeps you inside a budget. On the selling side it shows what reaches you. Rates differ between auction houses and countries, so type the ones in the auction’s terms. To see how much of a price is the metal itself, use bullion premium; to record what you paid, use collection catalogue.
How to use it
- Choose I am buying or I am selling.
- Type the hammer price and the rates from the auction’s terms.
- Read the total or net amount and the breakdown.
- When buying, type a budget to see the most you can bid.
What each setting does
- Buyer’s premium %: the fee added to the winning bid.
- Tax %: VAT, GST or sales tax. Choose whether it applies to the premium only, or to the hammer price plus premium.
- Shipping and insurance: a flat amount added to the total.
- Seller’s commission %: the share of the hammer price the house keeps.
- Fixed fees: listing, photo or insurance charges taken from the sale.
Worked example
You win a lot at 1,000. The premium is 20% (200) and 13% tax on the premium adds 26. With 15 shipping, you pay 1,241. With a budget of 1,241 the most you can bid is 1,000. If you sell at 1,000 with 15% commission (150) and 10 in fees, you receive 840.
FAQs
Is the tax always on the premium only? No. Some countries tax the whole price. Check the terms and use the matching option.
Are there other costs? Possibly: import duty, payment card fees, or a separate seller’s insurance. Add them to shipping or fixed fees.
Does this include tax on my profit? No. You may owe income or capital gains tax on a sale; ask a tax adviser.
Is anything stored? No. The sums run in your browser and nothing is saved.
Where the numbers come from
- Simple arithmetic on the rates you type. Premium, commission and tax rules differ by auction house and country; read the auction house's own terms of sale.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.