Buyer's Premium Confirmation Tool

FAQ

What does the buyer's premium confirmation tool do?

The tool confirms whether a price can already include a buyer's premium based on the auction bid increment. It also calculates the buyer's premium amount and the total price if the premium still needs to be added.

What should I enter as the hammer price?

Enter the price you want to test. This might be a reported auction sale price, a hammer price from an invoice, or another amount you are trying to classify as either pre-premium or premium-included.

What is the buyer's premium percentage?

The buyer's premium percentage is the fee added by the auction house to the hammer price. For example, if an item sells for a $100 hammer price and the buyer's premium is 20%, the premium is $20 and the total is $120 before any other taxes or fees.

What is a bid increment?

A bid increment is the step used for valid bids in an auction. If the bid increment is $5, valid hammer prices might be $5, $10, $15, $20, and so on. The calculator uses this to decide whether a backed-out pre-premium amount looks like a valid auction bid.

What does a positive result mean?

A positive result means the entered amount can include buyer's premium because the pre-premium amount backs into a valid bid increment. For example, $12 with a 20% buyer's premium and a $5 bid increment backs into a $10 hammer price.

What does a negative result mean?

A negative result means the entered amount does not appear to include buyer's premium under the bid increment you entered. The tool will show the premium that would be added if the entered amount is treated as the hammer price.

What does "could be either" mean?

Some amounts can be both a valid hammer price and a valid premium-included total. In that case, the calculator cannot determine the auction's pricing convention from one item alone. Try the calculator on another item from the same auction to help verify whether reported prices include buyer's premium.

Can this help with fair market value research?

Yes. Auctioneers, appraisers, dealers, bidders, and estate professionals can use the tool to review auction results, compare sale prices, estimate buyer's premium, and document pricing assumptions for fair market value research or resale analysis.

Does this include sales tax or other fees?

No. The calculator only evaluates buyer's premium against the entered hammer price, premium percentage, and bid increment. Auction houses may also charge taxes, shipping, handling, or Additional Fees that are not included here.

Why might results differ between auction houses and third-party aggregators?

Lot information received directly from an auction house may report hammer prices, buyer's premiums, and totals differently than a third-party auction aggregate. Some aggregates may display a price that already includes a buyer's premium from an auction house, while also showing a buyer's premium percentage as if a buyer had bid through the aggregate. Because of these reporting differences, the calculator may be inaccurate if the hammer price you enter already includes a buyer's premium that does not match the buyer's premium reported by the third-party aggregate.

Should I rely on this instead of the auction terms?

No. The tool is a convenience for checking auction math. Always verify calculations against the auction listing, bidder agreement, invoice, or auction house terms.

How does the buyer cost estimate calculate tax?

The invoice calculator applies the entered tax rate to hammer price plus buyer's premium, rounds that tax to cents, and then adds entered shipping, handling, and Additional Fees. This is one explicit estimate, not a universal tax rule. Check whether your auction house or jurisdiction taxes the premium or any of those fees differently.

How should I use a maximum bid ceiling?

Enter the full spending limit, premium and tax rates, known flat costs, and the auction's bid increment. The calculator estimates a raw limit, rounds down to a bid increment, and shows the estimated total and remaining budget at that bid. It does not model fees that change with price, tax on shipping, or an increment schedule that changes between bid ranges.

What does seller net proceeds include?

The seller-net estimate subtracts the entered commission percentage and fixed insurance, photography, shipping, and Additional Fees from the hammer price. Compare its assumptions with the signed consignment agreement, especially minimum commissions, unsold-lot charges, and fees not entered in the tool.

How does the basic calculator percent key work?

The percent key converts the current number based on context. For example, 200 + 10 followed by the percent key becomes 200 + 20, while 200 × 10 becomes 200 × 0.1. A standalone 25 becomes 0.25. The percent sign is a calculator key, not an operator to type into an expression. The page includes additional examples and keyboard guidance.

Where do historical currency and metal prices come from?

Historical currency rates are requested from Frankfurter. Precious-metal reference prices are requested from Metals.Dev, and Frankfurter may be used to convert the result when needed. Provider coverage and available dates vary. The tools display the date used and do not include bank spreads, metal purity, assay, dealer premiums, taxes, or auction fees.

How do I convert a metal weight to troy ounces?

Use the weight converter on the precious-metal page to convert between troy ounces, grams, kilograms, avoirdupois ounces, and pounds. One troy ounce is exactly 31.1034768 grams; one everyday avoirdupois ounce is 28.349523125 grams. Choose the units you have and want, then use the converted troy-ounce value in the metal-price calculator.

Why might a historical tool return a different date or no price?

Providers may not publish a new reference value on weekends, holidays, or dates outside their coverage. A returned date can differ from the date selected; check the displayed date before comparing results. Metals.Dev access also depends on a valid server-side key and the account's plan permissions. A provider outage, request limit, or missing historical value can prevent a result.

Are calculator entries sent to AuctionMath?

The buyer's premium, invoice, bid-ceiling, seller-net, and basic arithmetic calculations run in your browser. Basic calculator history is stored in that browser. Historical exchange-rate and metal lookups send the selected date, amount, and currency or metal codes to AuctionMath's API and the relevant data providers. See the Privacy Policy for storage and provider details.