# Guides

Plain-English explanations of the numbers behind every 17x7 calculator — the formulas term by term, worked examples with real figures, and the mistakes that cost people money.

## For online sellers

- [How Etsy Fees Work in 2026](https://17x7.com/guides/etsy-fees-explained/): Listing, transaction, processing, Offsite Ads, Share & Save and the fees that only apply outside the US — what each one is charged on, and three orders worked through to the cent.
- [How to Price Etsy Products for Profit](https://17x7.com/guides/how-to-price-etsy-products/): Start from what an item really costs you, decide what you need to keep, and work back to a list price that survives Etsy's fees — including orders that arrive through Offsite Ads.
- [Amazon FBA Fees Explained (2026)](https://17x7.com/guides/amazon-fba-fees-explained/): Size tier, shipping weight, price band, season and surcharge: the five things that set an FBA fulfillment fee, plus referral and storage fees, worked through on real boxes.
- [How to Calculate Amazon FBA Profit Margin and ROI](https://17x7.com/guides/amazon-fba-profit-margin/): Turn Amazon's fees into the numbers that decide whether a product is worth stocking — profit per unit, margin and return on investment — and see what moves them.

## For contractors and DIY builders

- [How to Calculate Roof Pitch, Rafter Length and Shingles](https://17x7.com/guides/how-to-calculate-roof-pitch/): From a level and a tape measure to a shingle order: how pitch, the pitch multiplier, rafter line length and roofing squares fit together, with three roofs worked through.
- [How to Estimate Deck Materials](https://17x7.com/guides/how-to-estimate-deck-materials/): A materials takeoff you can check by hand: rows of decking, cut-aware board counts, joists and hangers, fasteners, and the code span limits that decide joist size.

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Source: https://17x7.com/guides/ · Last updated: 2026-10-15