What is intervals.icu?
intervals.icu is a training analysis platform built by David Tinker, a software developer and cyclist in Cape Town. It started in mid-2018 as a side project (an analysis extension for Strava) and grew into its own thing; by 2024 it had passed 100,000 athletes and 111 million analysed activities, and Tinker went full time on it in September 2024. The site now counts 160,000+ active athletes. The company is Intervals.icu Ltd, with a London address, and the About page lists a core team of seven.
The unusual part is the business model. Everything most people come for is free with no trial clock and no card: fitness and fatigue modelling, interval detection, the workout builder, the calendar, power and HR analytics. The $4-a-month Supporter tier funds the work and adds a specific set of extras rather than gating the core.
Key Features
Fitness & Fatigue Modeling
The platform calculates your fitness (CTL), fatigue (ATL), and form (TSB) automatically from your training data. Watch your fitness build over time and optimize your training load to peak for events.
Power Analysis
For cyclists with power meters, intervals.icu provides detailed power curve analysis, training load tracking by power zones, and W' balance charts. Compare your power profile over different time periods and see how your fitness is developing.
Workout Builder
Create structured workouts with a visual editor. Build interval sessions, endurance rides, or complex training blocks, then export them to your head unit or sync them with other platforms.
Training Calendar
Plan your training weeks and months with a drag-and-drop calendar. Set weekly TSS targets, schedule workouts, and track your compliance with your training plan.
Who It's For
intervals.icu is ideal for:
- Self-coached athletes who want deep analytics without hiring a coach
- Data enthusiasts who read their own power curve for fun
- Budget-conscious athletes who can't justify expensive training platforms
- Cyclists and runners looking for better insights than Strava alone provides
How It Compares
TrainingPeaks Premium is $134.99 a year, or $19.95 month to month. intervals.icu gives you most of the same analysis for nothing, and its paid tier is $4 a month. The tradeoffs:
- It's a web app first. There's no native mobile app to match the TrainingPeaks one.
- It's a small team (seven people on the About page, with Tinker full time since 2024), and support runs through an unusually active forum rather than a help desk.
- Coaches will find far fewer of the integrations and client-management tools that TrainingPeaks is built around.
Is intervals.icu really free?
The core is free with no trial and no time limit: fitness and fatigue tracking, activity and interval analysis, the calendar and workout builder, power and HR analytics, multisport. The $4/month Supporter tier does add things, though, so "free" isn't quite the whole story: importing your full Strava history, the annual plan builder, advanced weather analysis (including a route weather forecast added in September 2026), fully custom zones, route matching and auto-flagged commutes, a customizable activity summary, CSV stream uploads, teams and coaching organisations, and beta access. The pricing page lists it at $4 a month, cancel any time.
How does it compare to TrainingPeaks?
You get comparable analysis for free, against $134.99 a year for TrainingPeaks Premium. TrainingPeaks has the better mobile app, far more coaching integrations, and a bigger ecosystem around it. For a self-coached athlete, intervals.icu often has the deeper analysis of the two.
Does it work with Garmin/Wahoo?
Yes, and you don't have to go through Strava to do it. intervals.icu connects directly to Garmin, Wahoo, Polar, Suunto, Coros and Zwift as well as Strava, so power, heart rate and everything else your device recorded comes in whichever route you pick. You can also upload FIT files by hand.
Can I plan workouts and sync to my bike computer?
Yes, and it can push them for you. Tick "upload planned workouts" in settings and intervals.icu sends the next week of your plan to Garmin Connect or to Wahoo Cloud, from where it syncs to the watch or head unit. You can also import or export a workout as a file: ZWO for Zwift, FIT, MRC and ERG.
