Training Zone Calculators, Compared
The FTP, threshold pace, and CSS math is public and the same everywhere. What differs is whether a tool needs a device or subscription, auto-detects your threshold from training data, and shows its work. Beetroot Pro is the free, no-device, transparent option; TrainingPeaks, Stryd, Garmin, and Coros add continuous device-driven zones at a cost.
This comparison is brand-neutral and factual. Each tool below is genuinely good at what it is built for.
| Feature | Beetroot Pro | TrainingPeaks | Stryd | Garmin / Coros |
|---|---|---|---|---|
| Free, no device requiredStryd needs a ~$219 foot pod; Garmin and Coros zones come from their watches. | ||||
| No account or login to use | ||||
| Cycling, running, and swimming in one tool | run-focused | |||
| Cycling FTP from a field test (20/8/ramp) | auto-detect | |||
| Running threshold pace zones | yes (Friel) | yes (Friel) | ||
| Running power zones | yes (rFTP) | yes (native CP) | ||
| Swimming CSS zonesGarmin/Coros report Swolf and pace, not a true CSS-band model out of the box. | manual | |||
| Sport-native zone systems (Coggan/Friel/CSS) | ||||
| Calculation method shown transparentlyStryd Critical Power and the watch auto-zone algorithms are proprietary. | ||||
| Shareable URL (no login) | ||||
| Printable coach-ready PDF zone sheet | export | |||
| Save zones to an account | ||||
| Auto-detect threshold from training historyThe platforms tied to your device data can estimate threshold continuously; a calculator needs you to enter a test result. | ||||
| Cost | Free | Free to ~$20/mo | ~$219 pod | Watch purchase |
Tool-by-Tool
Beetroot Pro® Training Zones
Free, no device, transparent math
A standalone calculator that turns a single field test into sport-native zones for cycling, running, and swimming. Built to be shared with a coach and to show the math rather than hide it.
Strengths
- One tool for FTP, threshold pace, and CSS, no device or subscription
- Sport-native models: Coggan power, Friel run pace, CSS-offset swim bands
- Formula is inspectable and the result is a shareable URL
- Printable coach-ready PDF and optional save-to-account
Trade-offs
- You enter a test result; it does not auto-detect threshold from training history
- No lab-grade or device-continuous measurement
Best for: Athletes and coaches who want quick, transparent, shareable zones from a test they already ran.
TrainingPeaks
Full training platform
The reference platform for structured training. Its zone calculator implements the Coggan and Friel models and ties zones into a full planning and analysis workflow.
Strengths
- Deep analysis, planning, and coach-athlete workflow
- Auto-updates threshold from uploaded workout data
- Multisport with established zone models
Trade-offs
- Best features sit behind a paid subscription
- Account required; not a quick shareable calculator
Best for: Athletes already committed to a structured plan and ongoing data analysis.
Stryd
Running power ecosystem
A foot pod plus power-modeling software built around Critical Power for runners. The most rigorous running-power zones available, within its own ecosystem.
Strengths
- Best-in-class running power and Critical Power modeling
- Continuous, terrain- and wind-aware power data
Trade-offs
- Requires buying the pod; running-centric (not a cycling FTP or swim CSS tool)
- Critical Power model is proprietary
Best for: Dedicated runners who train by power and want the most accurate run-power zones.
Garmin & Coros
Device platforms
Watch ecosystems that auto-calculate zones from your activities and physiology estimates. Zero manual math once the device knows you.
Strengths
- Automatic, always-on zone estimation from device data
- Multisport, integrated with the rest of your training metrics
Trade-offs
- Requires the watch; algorithms are proprietary and not shown
- Swim zoning is pace/Swolf, not a true CSS-band model
Best for: Athletes inside the Garmin or Coros ecosystem who want hands-off zones.
Get your zones in 30 seconds
Common Questions
Is a free FTP calculator as accurate as TrainingPeaks?
For turning a single test into zones, yes. The math behind FTP (95% of a 20-minute test), Friel run pace zones, and CSS is public and identical across tools. The difference is that TrainingPeaks also auto-updates your threshold from ongoing workout data, which a one-shot calculator cannot do. If you just ran a test and want zones now, the calculator is exact.
Do I need a Stryd to get running power zones?
No. Stryd gives the most accurate, continuous running power via its foot pod and Critical Power model. But if you have a 20-minute run-power number from any source, this tool estimates rFTP at 95% of it and builds Coggan-style power zones. It is an estimate, not a replacement for Stryd Critical Power, and the tool says so.
Why are my Garmin or Coros zones slightly different?
Device platforms use proprietary algorithms and often blend heart-rate, pace, and physiology estimates, and they auto-adjust over time. This calculator uses the published Coggan, Friel, and CSS models from one test result. Small differences are expected; both are valid, they just answer slightly different questions.
Which is best for triathletes?
For one place to set bike FTP, run threshold pace, and swim CSS from your test results and share them, this tool is the most convenient and is free. For continuous data-driven zone updates across a full season, a platform like TrainingPeaks paired with your devices is the stronger long-term home.