OneFreePlace
FREE ONLINE TOOL

Free Week Number
Calculator

Free advanced Week Number Calculator for ISO 8601, Sunday-start, Monday-start and custom week rules. Convert date to week, reverse week to dates, compare systems, inspect boundaries and export a full week-year table.

Open this tool in its own window ↗

FreeUse this tool without paying.No sign upStart with the tool right away.Clear stepsRead the tool’s own guidance.

About Free Week Number Calculator

Convert any date to ISO 8601 or other week numbering, reverse a week number back to its seven dates, compare systems side by side, inspect year-boundary surprises, navigate every week of a year and export a complete week table.

Workspace options

  • Date
  • First day of week
  • Minimum days in week 1
  • Week-year
  • Week

Available actions

  • Today
  • −1 week
  • +1 week
  • Jan 1
  • Dec 31
  • ISO 8601