# 17x7

> 17x7.com is a free set of calculators and developer utilities that show their work: Etsy and Amazon FBA fees, roof pitch, deck materials, time zones, cron, JSON Schema, YAML and robots.txt. Every calculator lists its arithmetic step by step, fee schedules are dated, and the tools run in the browser with no sign-up.

Results are estimates, not professional, tax or engineering advice. Every page also has a Markdown version for agents: add index.md to its path (for example https://17x7.com/tools/etsy-fee-calculator/index.md). Contact: hello@17x7.com.

## Calculators for sellers
- [Etsy Fee Calculator](https://17x7.com/tools/etsy-fee-calculator/): Every Etsy fee on one order — listing, transaction, processing, Offsite Ads — and what you actually keep.
- [Amazon FBA Calculator](https://17x7.com/tools/amazon-fba-calculator/): Size tier, fulfillment fee, referral fee and storage for one unit, with margin and ROI.

## Calculators for builders
- [Roof Pitch Calculator](https://17x7.com/tools/roof-pitch-calculator/): Pitch from rise and run (or angle) plus degrees, slope, rafter length, squares and shingle bundles.
- [Deck Material Calculator](https://17x7.com/tools/deck-material-calculator/): Boards, joists, hangers and screws for a rectangular deck — cut-aware, with the least-waste board length.

## Developer utilities (run in the browser)
- [Time Zone Converter](https://17x7.com/tools/time-zone-converter/): Convert one moment into up to 20 zones: DST gaps and repeats flagged, next clock changes, working hours, UTC math.
- [Cron Expression Generator & Explainer](https://17x7.com/tools/cron-expression/): Paste a cron expression for plain English, a field-by-field breakdown and next runs in any time zone, or build one.
- [JSON Schema Validator](https://17x7.com/tools/json-schema-validator/): Check JSON against a JSON Schema (2020-12, 2019-09, 07, 04): every error as a JSON Pointer, most specific first.
- [JSON Schema Generator](https://17x7.com/tools/json-schema-generator/): Paste sample JSON and get a draft 2020-12 schema with types, required keys and formats, checked against your sample.
- [YAML to JSON Converter](https://17x7.com/tools/yaml-to-json/): Convert YAML to JSON and back in your browser, with line-numbered warnings where YAML 1.1 and 1.2 disagree.
- [Robots.txt Tester](https://17x7.com/tools/robots-txt-tester/): Paste a robots.txt and test any URL: verdict, deciding rule and line, plus ten search and AI crawlers at once.

## Reference pages
- [Roof Pitch to Degrees Chart](https://17x7.com/tools/roof-pitch-calculator/pitch-to-degrees/)
- [Etsy Price Calculator (target margin)](https://17x7.com/tools/etsy-fee-calculator/etsy-price-calculator/)

## Guides
- [How Etsy Fees Work in 2026](https://17x7.com/guides/etsy-fees-explained/): Every Etsy fee explained: listing, 6.5% transaction, processing on the full checkout total, Offsite Ads and its $100 cap — with three worked examples.
- [How to Price Etsy Products for Profit](https://17x7.com/guides/how-to-price-etsy-products/): Build an Etsy price from real costs — materials, labor, postage and every Etsy fee. Target margin vs profit, Offsite Ads buffers and three worked examples.
- [Amazon FBA Fees Explained (2026)](https://17x7.com/guides/amazon-fba-fees-explained/): How Amazon sets FBA fees in 2026: size tiers, dimensional weight, price bands, the peak window, the 3.5% surcharge, referral and storage fees — with examples.
- [How to Calculate Amazon FBA Profit Margin and ROI](https://17x7.com/guides/amazon-fba-profit-margin/): Net proceeds, profit, margin and ROI for an FBA product step by step — why margin and ROI disagree, the $10 price band, packaging and costs fee tools miss.
- [How to Calculate Roof Pitch, Rafter Length and Shingles](https://17x7.com/guides/how-to-calculate-roof-pitch/): Measure roof pitch three ways, convert it to degrees, then work out rafter length, roof area, squares and shingle bundles — with IRC slope limits and examples.
- [How to Estimate Deck Materials](https://17x7.com/guides/how-to-estimate-deck-materials/): Count deck boards row by row, pick the board length that wastes least, then joists, hangers, rim boards and screws or clips — plus IRC joist span checks.

## For agents and developers
- [API & MCP docs](https://17x7.com/developers/): keyless JSON API and a remote MCP server (https://api.17x7.com/mcp, Streamable HTTP, no auth) for time zone conversion, cron explanations and the four calculators
- [OpenAPI 3.1](https://17x7.com/openapi.json): JSON API description
- [MCP server card](https://api.17x7.com/mcp/server-card): tools and transport metadata
- [Embeddable widgets](https://17x7.com/widgets/): free iframe calculators with a Powered by 17x7 link

## Optional
- [All tools](https://17x7.com/tools/)
- [About](https://17x7.com/about/)
- [Privacy](https://17x7.com/privacy/)
- [Terms](https://17x7.com/terms/)