The estimate is the auction house’s predicted hammer price range for a lot, expressed as a low estimate and a high estimate (e.g., “$1,500–2,000”). Estimates are based on comparable sales, condition, provenance, and market conditions at the time of sale.
Estimates serve two purposes: setting buyer expectations (so bidders don’t feel ambushed by reserves they can’t see) and establishing the reserve floor (typically the reserve is set at or near the low estimate). Lots that sell within or above the estimate range are “on estimate” or “over estimate”; lots that sell below are “under estimate.” Sustained under-estimate performance signals soft market conditions or estimate inflation.
Estimate-setting is one of the most consequential judgment calls an auction-house specialist makes. Set them too high and bidders skip the lot or it passes. Set them too low and the consignor feels cheated when a real result comes in higher. Estimate ranges typically have a 25–50% spread between low and high. Heritage Auctions and other major houses publish estimate-vs-result analytics in their post-sale reports as a transparency signal: high “sell-through within estimate” rates indicate accurate pricing, while consistent over-estimate or under-estimate results signal calibration drift.