Net proceeds are the sale price, minus your total selling costs, minus the mortgage balance retired at closing. Three of the costs are a percentage of the sale price, so they scale with it: agent commission, seller closing costs (title, escrow, attorney, recording), and transfer tax. Two are flat dollar amounts that do not: repairs and concessions agreed after the inspection, and what you spend preparing the place to list.
None of the percentages here is a national average, and this calculator does not claim one. They are starting points you are meant to replace with your own figures. Agent commission is negotiated in your listing agreement, and since the August 2024 changes to how buyer-agent compensation is handled, any remembered standard figure is worth even less than it used to be. Transfer tax varies by state, county, and city, and plenty of places levy none at all, so the calculator assumes none until you enter your own rate. Your listing agreement has the commission. Your title company or attorney can tell you the transfer tax and the closing costs where you are selling. Use their numbers, not ours.
For the mortgage payoff, use the payoff quote from your servicer rather than the balance on your last statement. They are not the same figure: a payoff includes interest accrued to the closing date, and sometimes a small fee.
The break-even sale price is the price at which net proceeds reach exactly zero. Because the percentage costs scale with the price and the flat costs do not, it has a closed form: add your flat costs to your mortgage payoff, then divide by one minus the combined percentage rate. It is a property of your cost structure and your payoff, so it does not change when you move the sale price slider.
Net proceeds can be negative, and the calculator shows it negative rather than hiding the case. A seller whose payoff and costs exceed the sale price has to bring money to the closing table, and that is worth knowing early.
What this does not include: capital gains tax (most people selling a primary residence fall under the IRC section 121 exclusion, and tax is out of scope here), prepayment penalties on your mortgage, HOA transfer or resale-certificate fees, property-tax proration and any escrow refund, second mortgages or HELOC balances beyond what you enter as the payoff, and moving costs. Treat the total as the large, predictable part of the bill rather than the whole of it.
Related reading: Hidden Costs of Buying a Home