ZWO vs FIT: Workout File Formats Compared

What is the difference between ZWO and FIT workout files? Simply put: ZWO is for Zwift, and FIT is for Garmin/Wahoo devices.

While both file types store "structured workouts" (intervals, targets, durations), they speak different languages.

Quick Comparison

Deep Dive: ZWO

ZWO files are flexible because they use relative power.

• A ZWO file says: "Ride at 95% of FTP."
• It doesn't care if your FTP is 100W or 400W. Zwift calculates the target when you load the workout.
• Advantage: You never need to edit the file when your fitness changes.

Deep Dive: FIT

FIT files (for workouts) usually use absolute values.

• A FIT file says: "Ride at 250 Watts."
• Disadvantage: If your FTP goes up, that 250W interval becomes easier. You often need to update/re-sync the file.
• Note: Some modern devices support %FTP in FIT files, but absolute watts remain the most compatible standard for conversion.

Converting Between Formats

Because they handle power differently, you need a converter to translate them.

ZWO to FIT

Use Case: Taking a Zwift workout outdoors.

• The converter asks for your current FTP.
• It calculates the absolute watts (e.g., 95% * 300W = 285W).
• It writes a FIT file with "285W" as the target.
• Use the ZWO to FIT Converter

FIT to ZWO

Use Case: Riding an outdoor file indoors.

• The converter analyzes your raw power data.
• It asks for your FTP at the time of the ride.
• It reverse-engineers the intensity (e.g., 285W / 300W = 95%).
• It writes a ZWO file with "0.95" as the target.
• Use the FIT to ZWO Converter

Summary

• Use ZWO for Zwift.
• Use FIT for everything else (Garmin, Wahoo, etc.).
• Use our converters to switch between them.

Related Guides

• What is a ZWO File?
• Garmin FIT Files Guide