Interval Timer

Create and run structured interval workouts using a compact expression editor.

I created this app because I hated how all the other interval timers worked. They take way too long to build a workout and don't visually represent workout progress well.

This timer is great for gym workouts or treadmill intervals.

Quick Start

1. Enter an expression in the editor (e.g. 5x(1mWork+30sRest)).
2. Include Work and/or Rest steps.
3. Press Start.

Start stays disabled until the expression is valid.

Expression Basics

• Add steps with +: 10mWork+5mRest+10mWork
• Repeat with Nx(...) (or N(...)): 6x(1mWork+1mRest) or 6(1mWork+1mRest)
• Nest repeats: 3x(5x(30sWork+30sRest)+1mRest)
• Use mixed time units: 1h5m30s or 1m30s
• Ramp inside a repeat with ..: 4x(30s..60sWork+30sRest) expands to 30s, 40s, 50s, 60s.
• Trim last expanded step with #: 3x(2x(60sWork+60sRest#)+2mRest) trims the last 60sRest so you don't actually end up with 3m rest between each working set.

Important Behavior

• Work or Rest without a duration creates a hold step.
• Hold steps do not auto-advance; press Lap button to continue.
• Lap button skips to the next step.
• Reset stops and clears the current run state.
• Step labels can be edited from the step strip while paused/not running.
• The timer keeps running even if your phone is off. If you accidentally close the tab or browser while the timer is running it doesn't matter.

Presets, Library, and Cues

Open the presets dropdown to:

• Load templates or recent expressions
• Save, search, or mark items as favorites
• Keep the screen awake while the timer is running
• Toggle cues (5s Start Countdown, Sound, Haptic)

Keyboard Shortcuts (Desktop)

All typical keys should work including:

• 0 - 9, x, +, (, ), BACKSPACE, and del

In addition to the typical keys the following keys also work:

• * = multiply x
• : = minutes:seconds (for example 1:30)
• .. = sequence ramp inside Nx(...)
• # = trim the last expanded step from the preceding Nx(...)
• h = hour(s)
• m or ' = minute(s)
• s or " = second(s)
• w = Work
• r = Rest
• HOME = SOL
• END = EOL
• ← or → = move left/right one caret
• CTRL + ←/→ = move left/right whole segment