Find the ISO week number for any date
FAQ
What is an ISO week number?
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About Week Number
Week Number was built for the moment you just need to handle this task and move on — no signup, no upload to a third-party server. The goal was to keep the path from "open the page" to "get the result" as short as possible. No mandatory account, no cookie wall, no upsell at every step. It pairs naturally with the other utility utilities here when you need to chain a quick workflow.
When you'd reach for Week Number
You're cleaning up a folder of files that accumulated over a project and need to standardize them.
Designers, writers, and developers wrapping up deliverables.
Drop each file in, copy the output, move on.
You're hitting the daily limit of a paid SaaS and need a backup option for a single quick job.
Marketers and ops people whose primary tool is metered.
Stay productive without burning credits.
You're on a public or shared machine and don't want to leave traces of what you're working on.
Travelers, contractors, anyone working from a friend's computer.
Nothing is uploaded, nothing persists if you're not signed in.
You need to handle a one-off task right before a meeting and don't have time to install anything.
Anyone working remotely on a borrowed or restricted machine.
Open the page, get the result, paste it into your doc — under a minute.
Frequently asked about Week Number
- Is Week Number really free?
- Yes — Week Number is free for unlimited personal use, with no account required and no watermark on the output.
- What browsers does Week Number support?
- Every modern browser released in the last three years: Chrome, Firefox, Safari, Edge, Brave, Opera.
- Will Week Number change my original file?
- Never. Week Number only reads your input file and produces a new output file.
- Are my files uploaded to a server when I use Week Number?
- Week Number processes everything in your browser using local APIs. Your files never leave your device.
- Does Week Number work on mobile?
- Yes, Week Number is fully responsive and tested on iOS Safari and Android Chrome.