All tools
Every 17x7 calculator and utility, grouped by who uses it. Each one runs in your browser and shows the arithmetic behind its answer.
For online sellers
For contractors and DIY builders
Roof Pitch Calculator
Pitch from rise and run (or angle) plus degrees, slope, rafter length, squares and shingle bundles.
atan(6 ÷ 12) = 26.57°
Deck Material Calculator
Boards, joists, hangers and screws for a rectangular deck — cut-aware, with the least-waste board length.
⌈144″ ÷ 5.6875″⌉ = 26 rows
For developers and AI agents
Time Zone Converter
Convert one moment into up to 20 zones: DST gaps and repeats flagged, next clock changes, working hours, UTC math.
UTC = local − offset
Cron Expression Generator & Explainer
Paste a cron expression for plain English, a field-by-field breakdown and next runs in any time zone, or build one.
*/15 9-17 * * 1-5
JSON Schema Validator
Check JSON against a JSON Schema (2020-12, 2019-09, 07, 04): every error as a JSON Pointer, most specific first.
valid(instance, schema)
JSON Schema Generator
Paste sample JSON and get a draft 2020-12 schema with types, required keys and formats, checked against your sample.
{ "a": 1 } → "integer"
YAML to JSON Converter
Convert YAML to JSON and back in your browser, with line-numbered warnings where YAML 1.1 and 1.2 disagree.
country: NO → false
Robots.txt Tester
Paste a robots.txt and test any URL: verdict, deciding rule and line, plus ten search and AI crawlers at once.
Allow: /a/b > Disallow: /a
No tool matches that search — try a shorter word, or tell us what you were looking for.
Reference pages
What makes a 17x7 tool
Each calculator is built around one job that people do for real money or real materials — pricing an Etsy listing, checking whether an Amazon product still makes money after fees, ordering shingles, buying deck boards. We would rather do a handful of these properly than publish hundreds of thin converters.
Every page explains the formula, walks through a worked example, lists the limits of the method, and answers the questions people actually ask. Numbers that change — marketplace fees, code tables — carry a source and the date we last checked it.
Missing a calculator you need for work? Tell us what it should do.