90/15 Deep Work Timer — free, with music
90/15 is the deep work split: ninety minutes on one hard thing, fifteen minutes of real recovery. The length lines up with the ultradian rhythm — the roughly 90-minute cycles your alertness moves through during the day — and with how long it takes to get somewhere on genuinely difficult work.
This is the block for the work that doesn't fit anywhere else: architecture decisions, proofs, long-form writing, anything where interruption cost is measured in half-hours. One 90-minute block with the phone in another room routinely beats an afternoon of supervised multitasking.
Ninety minutes is demanding, and that's the point — most people get two, maybe three of these blocks per day. Don't stack five. If you can't hold ninety yet, 50/10 is the honest on-ramp.
Questions
Is this 90/15 timer free?
Yes. The timer on this page runs in your browser with no account and no ads. The full Flow app also has a free tier — the paid plan adds the full music library and extra ambient sounds.
Does the timer keep running if I switch tabs?
Yes. The countdown keeps going in the background and the remaining time shows in the tab title, so you can work in another window.
What is the 90/15 method?
You work in fixed blocks: 90 minutes on a single task, then a 15-minute break, then repeat. The fixed end point makes it easier to start, and the break keeps the next block usable.
Where is the music?
This page is the bare timer. The Flow app pairs the same presets with original focus music produced in-house by Virzy Guns — not stock loops — plus an ambient mixer for rain, café, and similar layers.
Other splits
The full setup is one click away
This page is the timer on its own. The app adds original focus music — produced in-house, not stock loops — an ambient mixer, tasks, and honest stats. Free tier, no sign-up to try.