How to Calculate Your Max Bid Before You Buy for Resale

"I'll go up to $150" is a guess dressed up as a plan. It usually comes from a gut feeling about what the item might be worth, minus a vague sense that you should probably leave some room for profit. That's not a ceiling — it's a number you'll talk yourself past the moment the bidding gets close.

A real max bid comes from working backward from three things you actually know: what the item is likely to resell for, what the platform will take in fees, and the profit margin you're not willing to go below. Here's the actual math.

The formula

Start with the resale value — a real estimate based on recent comparable sales, not an asking price. From there:

1. Subtract platform fees. eBay runs around 13% of the sale price, Etsy around 9%, Reverb around 8%, Facebook Marketplace effectively 0%. This comes off the top before anything else.
2. Subtract your target profit. Decide your margin up front — a percentage of the resale value you won't sell below — and take it out of the budget before you ever place a bid, not after.
3. What's left is your budget. Resale value, minus fees, minus target profit.

A $200 item with a 13% fee and a 30% target margin: $200 − $26 (fees) − $60 (profit) = $114 budget. That's the most this item can cost you and still hit your number — before the last step.

Auctions and fixed-price sales use different math

That $114 isn't always your max bid — it depends on where you're buying.

At a traditional estate sale, the tag price is the price. Your budget is your max bid.

At an auction (CTBids, EBTH, AuctionNinja, or an EstateSales.NET marketplace listing), the winning bid isn't what you pay — a buyer's premium gets added on top, typically 10-20%. That premium has to come out of the same budget, not on top of it, or you'll blow past your real ceiling the moment you win. The correct max bid is your budget divided by (1 + premium), not your budget minus a flat guess:

$114 budget ÷ 1.15 (a 15% premium) = $99 max bid — because $99 plus 15% buyer's premium lands you right back at $114 out of pocket.

Skip that division and bid your full $114 at an auction with a 15% premium, and you've actually agreed to pay $131 — $17 over budget before you've sold a thing.

What this doesn't cover

This formula gets you a real number, but it isn't the whole cost. It doesn't account for shipping, packing materials, or sales tax on the purchase — those come out of your margin later, not before you bid. (More on why that matters in hidden costs that eat into resale profit.) Treat the max bid as your ceiling on the purchase price, not a guarantee of the profit you'll actually walk away with.

Do the math before you're standing in front of the item

Working this out in your head while an auction clock is running, or while someone else is already reaching for the tag, is exactly when the math gets skipped. WorthAPick has a free max bid calculator — no signup required — or, if you're pricing items you've already scanned, it runs the same calculation automatically against the estimate, using the right formula for whether the listing is an auction or a fixed price sale. Set your target margin once, and every item you check shows its ceiling, not just its estimated value.