The most common mistake in a marketplace P&L is comparing a gross selling price with net costs. Commission is charged on the gross price including VAT, while your cost of goods is net. This calculator converts the price to net using your VAT rate, then subtracts commission calculated on gross — which is what actually leaves your account.
| Advertising % | Ad spend as a share of net revenue on that channel — the inverse of ROAS. 8% equals 12.5× ROAS. |
| Returns % | The share of revenue lost to returns you cannot resell, plus the return shipping you absorb. In apparel this is often the largest single cost after the goods themselves. |
| Min price for 20% | The gross price you would need on that channel to clear a 20% net margin at the costs you entered. If it is above what the market pays, that channel does not work for this product. |
Because hard-coded rates go stale. Allegro and Amazon revise their commissions several times a year and both charge different rates by category — a tool that tells you ‘Allegro is 11%’ with confidence is wrong most of the time. The defaults here are a starting point. Enter the rate from your own settlement report and the answer becomes real.
Deciding which channel to open is a margin question before it is a marketing question. We have told clients not to launch on a channel because the arithmetic did not work at their cost base — that conversation goes faster with a table than with an opinion. The full version, with your real settlement data across every channel, is part of the Store & Channel Audit.