Revenue is counted excluding GST: price ÷ (1 + GST%). GST isn't your money.
Referral fee uses the actual customer-paid price. Amazon fees are entered excluding fee GST, assuming you can claim eligible input credit; otherwise include unrecoverable tax in other costs.
Returned orders are assumed fully refunded and resellable. Enter the complete extra net loss per return, including unrecovered shipping, fees, handling and damage. Check this against actual settlements.
Ad spend per placed order is ad spend % × GST-inclusive selling price. Match this to ad spend divided by gross placed-order value, not post-return net sales.
Contribution is an estimate per order placed, averaged over expected returns, before fixed costs. The monthly result is contribution × orders minus the fixed costs you enter. It excludes any other costs you omit.
Reading your result
Positive contribution: the SKU covers the variable costs entered; check the monthly result before scaling.
Negative contribution: every additional order at these assumptions increases the loss.
Break-even ad spend % is the estimated ceiling before per-order contribution reaches zero. It does not cover fixed costs.
Fees vary by category, price and fulfilment method. Check the current values in Seller Central. Amazon fee guide.
