A pyramid climbs and comes back down. A session built around a target pace has a long first effort and shorter ones after it. A timer that only takes one work value and one rest value forces you to either simplify the session or run three timers in a row, and both are worse than the session you meant to do.
cronoWiz lets a program hold rounds of different lengths, with their own recoveries, and reads out what is coming next while you are still in the current one. Ready-made shapes are there — easy, tempo, pyramid, fartlek, HIIT — and you can build your own from scratch.
If you pair a Bluetooth chest strap, the intervals sit next to your heart rate and its zone, so you can see whether the recovery was long enough before the next effort starts rather than after. Without a strap it estimates the curve instead, and says so.
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Rounds that differ
each block has its own work and rest, so a pyramid stays one session instead of three.
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It says what is next
the upcoming interval is announced before the current one ends.
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Heart rate beside the clock
with a Bluetooth strap, zones are live; without one it estimates and labels the estimate.
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Treadmill control
on an FTMS machine the program can drive speed and incline instead of asking you to.
Building a pyramid without running three timers
A pyramid is the clearest case of why one work value and one rest value are not enough: 1-2-3-2-1 minutes with matched recoveries is nine efforts of five different lengths. On a single-interval timer you either flatten it into 2-2-2-2-2, which is a different session, or you start and stop three timers and lose the transitions.
In cronoWiz a program is a list of blocks, and each block carries its own work and rest. You add the five efforts, set the recovery for each to match the effort before it, and save the whole thing as one preset. The timer then reads out the next interval while you are still inside the current one, which is when you need to know it — hearing “three minutes next” with forty seconds of recovery left changes how you spend those forty seconds.
The ready-made shapes cover the common ones — easy, tempo, pyramid, fartlek, HIIT — and each is editable, so the fastest route to your own session is usually to open the nearest shape and change the numbers rather than to start from an empty program.
Reading the recovery instead of guessing at it
The question a HIIT session actually asks is whether the recovery was long enough, and the honest answer is not how you feel at the end of it — it is where your heart rate got to. Standing there judging it by breath is how a session drifts into a tempo run by round four without anyone noticing.
With a Bluetooth chest strap paired, the interval and the heart rate sit on the same screen, with the zone labelled. What you are watching for is the number at the end of the recovery, not the peak: if it has not come back down before the next effort starts, the next effort is not the effort you planned.
Without a strap cronoWiz estimates from the Tanaka curve and your current speed and incline, and labels the number as an estimate rather than presenting it as measured. It is enough to see the shape of a session; it is not enough to set training zones from. Connect a strap and the real reading takes over immediately.
On a treadmill or bike that speaks FTMS over Bluetooth, the program can set speed and incline itself, which removes the other place these sessions leak: the ten seconds spent turning a dial at the start of every interval.
Free. Private. Yours.
No account. No server. No cookies. Just you, your phone, and an app that minds its own business. cronoWiz is a free PWA that runs entirely on your device — your data never leaves. Ever.
The questions people actually ask
How is this different from a Tabata timer?
Tabata is one fixed shape: 20/10 for eight rounds. HIIT is a family of shapes, and the useful ones rarely repeat the same interval — which is exactly what a single work/rest pair cannot express.
Can I use it on a treadmill?
Yes, and if the treadmill speaks FTMS over Bluetooth the program can set speed and incline itself. Otherwise it just calls the changes and you turn the dial.
Do I need a heart-rate strap?
No. Without one cronoWiz estimates heart rate from the Tanaka curve and your current speed and incline. The estimate is labelled as such, and a real strap overrides it the moment you connect one.