Intervals.icu vs TrainingPeaks: Free Analytics or the Industry Standard in 2026?

TL;DR: Intervals.icu vs TrainingPeaks is the most common platform question in endurance sport, and the answer has become surprisingly clear. For self-coached athletes who want analytics, Intervals.icu wins: the fitness chart, power curve and interval analysis that TrainingPeaks puts behind its roughly 20 dollar per month Premium tier are free on Intervals.icu, with an optional 4 dollar Supporter tier. For coached athletes and coaches building a business, TrainingPeaks wins: the coach network, the marketplace with 70,000+ plans sold, and 35+ federation partnerships have no equal. What neither platform offers is physiological testing, structured coach-athlete communication with an AI assistant, or a professional testing-to-training workflow. Coachbox closes that gap: AI-powered lactate testing with LT1/LT2 detection in under 60 seconds, zones that update automatically, and a coaching platform localized in seven languages, from EUR 12.95 per month.

The Case for Intervals.icu

Intervals.icu is the free tool that made paid analytics justify themselves. Built by David Tinker, a developer and cyclist in Cape Town, it started in 2018 as a side project for analyzing his own Strava data and grew into a platform with 160,000+ active athletes and 193 million+ analyzed activities. Tinker went full-time on it in 2024, funded by voluntary supporter subscriptions rather than investors.

The Analytics Are Free, and They Are Better

The core argument for Intervals.icu is blunt: the analysis features endurance athletes actually use cost nothing. Fitness, fatigue and form tracking (the CTL/ATL/TSB model), a multi-season power curve with several models (eFTP, Morton’s 3-parameter, Monod and Scherrer), automatic interval detection with spike correction, decoupling analysis, zone time distribution and a structured workout builder are all in the free tier, no credit card, no expiry.

On TrainingPeaks, the equivalent features live behind Premium at around 20 dollars per month for athletes. The comparison is so direct that Intervals.icu’s own testimonials include athletes who cancelled TrainingPeaks Premium and became supporters instead. The optional Supporter tier costs 4 dollars per month and adds extras: an annual training plan builder, full Strava history import, fully custom zones, weather analysis, and teams for coaching organisations.

Customization Without Limits

Beyond the standard charts, Intervals.icu lets users define custom fields, build custom charts with Plotly, and even write JavaScript inside the platform to compute new metrics from raw FIT data. The open API (OAuth 2.0, webhooks, free) has attracted 250+ third-party integrations. For athletes and coaches who think in data, no platform at any price offers more freedom.

A Community That Ships

Development happens in public on the Intervals.icu forum. Users request features, the developer responds personally, and improvements arrive continuously. The platform is available in 21 community-translated languages, and it connects to Garmin, Polar, Suunto, COROS, Wahoo, Strava, Zwift, MyWhoosh, Rouvy, Oura, Whoop and Concept2, among others.

For the full picture, see our Intervals.icu Review.

The Case for TrainingPeaks

TrainingPeaks has been the reference platform of structured endurance training for two decades, and its advantages are the kind that take decades to build.

The Shared Language of Endurance Coaching

TSS, CTL, ATL and TSB are TrainingPeaks inventions that became the vocabulary of the sport. Intervals.icu implements the same concepts well, but when a coach and athlete discuss form before a race, they are usually speaking TrainingPeaks. The Performance Management Chart remains the de facto standard for load management in cycling, triathlon and running.

The Coach Network and Marketplace

This is the argument Intervals.icu cannot answer. If you hire a coach, odds are they deliver through TrainingPeaks. The coach-athlete workflow has twenty years of refinement, the Training Plan Marketplace has sold 70,000+ plans, Coach Match funnels athletes to accredited coaches, and 35+ national federations, from USA Cycling to British Cycling and Belgian Cycling, standardize on the platform. For a coach building an international business, this reach is the product.

A Finished Mobile Experience

TrainingPeaks’ mobile apps are consistently rated ahead of Intervals.icu’s, which remains web-first with a basic mobile app. For athletes who log, review and communicate from their phones, this difference is daily, not cosmetic.

The Cost of the Standard

The price is the recurring objection: Premium for athletes runs around 20 dollars per month (about 135 dollars per year), and coach plans run $21.99 to $54.99 per month plus per-athlete fees, in USD, English-only. Our TrainingPeaks Review and TrainingPeaks Pricing cover the details.

Where Both Fall Short

Different as they are, Intervals.icu and TrainingPeaks share the same blind spots, and they matter most to working coaches.

Neither Has Physiological Testing

Neither platform can analyze a lactate step test, detect LT1 and LT2 from measured values, or generate training zones from a physiological assessment. Intervals.icu estimates FTP cleverly from field data, and TrainingPeaks tracks thresholds you enter, but a coach who tests athletes runs the analysis in separate software and types the resulting zones in by hand. Every retest repeats the ritual. For coaches who test quarterly across a roster, that is hours of error-prone administration per season.

Neither Has an AI Assistant

Both platforms accumulate enormous athlete datasets and leave every conclusion to the human reading the charts. Neither can review a week, flag an overtraining pattern, or draft the next block from an athlete’s actual data.

Intervals.icu Is Not a Coaching Business Platform

Coaches can work in Intervals.icu, and some do, but there is no billing, no invoicing, no branded client reports, no guided athlete app, no education, and support is a community forum rather than a service. The interface’s learning curve is a real adoption barrier for non-technical athletes, and the whole platform rests on one developer, brilliant and responsive as he is.

TrainingPeaks Still Lacks Real Communication

No real-time messaging means coaching conversations spill into WhatsApp and email, fragmenting the record of the coach-athlete relationship. And the per-athlete pricing model means a growing roster grows the bill linearly, which taxes exactly the success a coaching business works for.

The Multi-Tool Stack

A coach who wants deep analytics, professional delivery, real communication and physiological testing ends up running two or three platforms plus a messaging app plus testing software. Each seam between tools costs money, time and data integrity.

The Case for Coachbox

Coachbox was built for the workflow both platforms leave unfinished: professional endurance coaching grounded in physiological testing.

Testing Inside the Coaching Loop

Run a lactate test and Coachbox handles the rest: enter values from any lactate meter, the AI interprets the curve and detects LT1 and LT2 in under 60 seconds, zones update automatically in the athlete’s profile, future workouts use the new zones, and a branded PDF report is ready for the athlete. Every coaching plan includes a set of free tests at signup, with per-test pricing after that. When a test takes minutes instead of an evening, testing becomes a regular service instead of an occasional project.

AI That Knows Your Athletes

Coachbox AI is an assistant connected to your athletes’ real workouts, metrics and zones. Ask it to review a session, check for warning signs, or summarize how an athlete absorbed the last block, and it answers from the data with a critical, evidence-based take. It is the interpretation layer that both Intervals.icu and TrainingPeaks leave entirely to you.

A Complete Coaching Platform

Around the testing core, Coachbox covers the full workflow: training calendar with annual periodization, structured workouts that sync to Garmin, Wahoo, Polar, Suunto, COROS, Fitbit and TomTom (Zwift and Rouvy coming soon), load tracking, in-app messaging, wellness monitoring, the Coachbox Academy for coach education, and matchmaking that connects athletes seeking a coach with coaches on the platform.

European, Multilingual, Transparent

Coachbox prices in EUR from 12.95 per month with plans up to Summit at 69.95, athletes always use the app for free, and there is a 14-day trial without a credit card. The platform is fully localized in seven languages (English, Dutch, French, German, Italian, Spanish and Portuguese) and counts 25,000+ users with 11 million+ workouts logged across 15+ countries.

For the direct comparisons, see Coachbox vs Intervals.icu and Coachbox vs TrainingPeaks.

Three-Way Comparison Table

Real Coaching Scenarios

Scenario 1: Self-Coached Cyclist Who Loves Data

You train yourself, own a power meter, and spend rest days reading your own charts. You have no coach and no plans to hire one.

Best choice: Intervals.icu. It was built by someone exactly like you, for exactly this. Free, deep, endlessly customizable. Becoming a supporter at 4 dollars per month is a fair thank-you.

Scenario 2: Athlete Working with a TrainingPeaks Coach

Your coach delivers plans through TrainingPeaks, reviews your files there, and your federation program standardizes on it.

Best choice: TrainingPeaks. The platform your coach works in is the right platform. Many athletes in this position run a free Intervals.icu account alongside for personal analysis, which costs nothing and adds depth.

Scenario 3: Coach Who Tests Athletes

You coach 15 to 40 endurance athletes, run lactate step tests every 8 to 12 weeks, and currently juggle a delivery platform, a testing spreadsheet and hand-built PDF reports.

Best choice: Coachbox. Testing flows into zones and prescriptions automatically, the AI handles threshold detection, and branded reports replace the handmade ones. Neither Intervals.icu nor TrainingPeaks supports any part of this workflow.

Scenario 4: European Coach with a Mixed, Multilingual Roster

You coach in the Benelux with Dutch-, French- and English-speaking athletes of varied technical ability, price in euros, and want to add testing as a paid service.

Best choice: Coachbox. Athletes each get the app in their own language, EUR pricing keeps the business simple, and integrated testing makes the new service practical. Keep a free Intervals.icu account for your own training if you like; the two coexist happily.

Who Should Choose What

Choose Intervals.icu if you are…

• A self-coached athlete who wants the deepest free analytics in the sport
• A data enthusiast who builds custom charts and metrics
• A coach of technical athletes happy with a shared data workbench and a 4 dollar Supporter tier
• Budget-driven above all: nothing else comes close at the price

Your stack: Intervals.icu for everything analytical. Add separate tools if billing, testing or client reporting enter your practice.

Choose TrainingPeaks if you are…

• An athlete whose coach or federation lives on TrainingPeaks
• A coach building revenue through the plan marketplace and Coach Match
• Committed to the TSS/CTL/ATL vocabulary as your shared language
• Reliant on the most polished mobile app of the three

Your stack: TrainingPeaks for delivery, a messaging app for communication, and separate testing software if you test.

Choose Coachbox if you are…

• A professional endurance coach, especially one who tests athletes or wants to start
• Tired of manual zone entry between testing tools and delivery platforms
• Coaching athletes who need a guided app in their own language
• Interested in an AI assistant grounded in your athletes’ actual data
• Consolidating two or three tools into one EUR subscription

Your stack: Coachbox for testing, planning, communication and client deliverables in one place.

The Bigger Picture

Intervals.icu versus TrainingPeaks is really a question about who does the coaching. If you coach yourself, Intervals.icu has quietly won this matchup: the analytics are free, deeper, and improving faster. If someone else coaches you, or you coach others inside the TrainingPeaks economy, the ecosystem still rules, and the subscription is the cost of belonging to it.

The question neither platform answers is what professional coaching increasingly runs on: measured physiology. Zones on both platforms are estimates or hand-typed numbers, tests live in other software, and the interpretation burden sits entirely on the coach. That is the gap Coachbox occupies: not freer than Intervals.icu, not bigger than TrainingPeaks, but the only one of the three where a lactate test becomes accurate zones, an updated plan and a client-ready report in the same platform, in the athlete’s own language.

Pick by where your training truly lives: in your own charts, in the industry ecosystem, or in a testing-driven coaching practice that deserves one platform instead of three.