Calculator Inputs and Outputs
Inputs
- Date — example: 2026-07-28
- Week starts on — example: 1
Results
- Week start date
- Week end date
- ISO week number
Formula used
The selected date is moved backward to the chosen start of week.
How to Use the Week Start Date Calculator
Enter the requested values, check the units and assumptions, then select Calculate Week Start Date. The built-in defaults provide a complete working example.
Formula
The selected date is moved backward to the chosen start of week.
Understanding the Results
The primary answer appears first. Supporting outputs show related quantities, conversions, dates, costs, ratios, or intermediate values. Calculations keep additional precision before display rounding.
Accuracy Tips
- Use measured values and consistent units.
- Review assumptions, rates, timing, and efficiency inputs.
- Recalculate after changing any condition.
Important Note
This tool provides an informational estimate. Confirm critical financial, medical, construction, scientific, tax, legal, or safety decisions with an appropriately qualified professional.
Calculation Standards
This tool uses documented formulas and high-precision internal values. Displayed results may be rounded for readability. Review the assumptions and verify important decisions with a qualified professional.
Read our calculation methodology