Hey there. I'm a reseller. I've been flipping finds from Craigslist and Facebook Marketplace for a few years now — everything from furniture and electronics to clothing and random stuff people just want gone. What started as a side hustle to pay off some debt turned into a real income stream, and along the way I learned that the difference between a profitable flip and a break-even one often comes down to one thing: which platform I sell on.
Here's the thing that drove me crazy. Every time I found something worth flipping, I had to open five different browser tabs and visit five different fee calculators to figure out where I'd make the most money. eBay's calculator only shows eBay fees. Mercari's help page tells you about Mercari. Poshmark, Etsy, Facebook — same story. None of them talk to each other. I was doing mental math, scribbling numbers on sticky notes, and honestly making mistakes that cost me real money.
One time I sold a vintage camera on eBay for $80 that I'd bought for $30. I thought I was clearing $50 minus a small fee. After eBay's 13.6% final value fee, the per-order charge, and shipping, I walked away with way less than I expected. Had I listed the same camera on Mercari, I would have paid about $8 in fees instead of $12+. On Facebook Marketplace with local pickup, I would have paid zero. That $4–12 difference matters when you're doing volume.
So I built FlipMargin. It started as a spreadsheet, then a messy side project, and now this. The idea is simple: enter what you paid and what you're selling it for, and see all five platforms compared side by side. No more tab-switching. No more mental math. The calculator shows you fees, net payout, profit, margin, and ROI for eBay, Mercari, Poshmark, Etsy, and Facebook Marketplace all at once, and highlights which one pays you the most.
I also added a target profit mode because sometimes you work backwards — you know you need to make $20 on this flip, and you want to know the minimum price to list at on each platform to hit that target. That came directly from my own workflow: I'd find something for $15 at a garage sale, decide I wanted to double my money, and then need to figure out the list price that accounts for each platform's different fee structure.
Beyond the calculator, I wanted FlipMargin to be a genuinely useful resource. Each platform has its own dedicated page with a deep dive on how the fees work, edge cases to watch for, and a build-time fee table at different price points. I wrote all of that content myself based on my own experience and research, and I keep the fee data updated. You'll see a "Fees verified" date near every calculator — that's the last time I confirmed the rates against each platform's official documentation.
A few important caveats: I'm not affiliated with any of these platforms. Fee rates change, sometimes without much notice. The calculators on FlipMargin are reference tools — they give you a fast, reliable comparison, but you should always verify current fees on the platform's own seller help pages before making final pricing decisions, especially on high-value items where a small rate change means real money.
FlipMargin is free to use. I run ads through Google AdSense to cover hosting and domain costs. No accounts, no logins, no data collection beyond what's described in the privacy policy. Just a tool I wish had existed when I started flipping.
If you find FlipMargin useful, tell another reseller. If you spot a fee that's out of date, drop me a message and I'll update it. Happy flipping.