Predicting FTP from Short-Duration Tests: Accurate Estimation Without Riding a Full Hour

The Definition of FTP and the Challenge of Testing

FTP (Functional Threshold Power) is theoretically defined as the maximum power you can sustain steadily for about one hour. The problem is that riding a full hour at maximum effort is extremely painful and requires well-honed pacing experience. Most riders—including many professionals—cannot accurately complete a one-hour all-out effort in an isolated testing environment.

As a result, various short-duration tests have emerged, attempting to predict this one-hour value using shorter all-out efforts.

Method 1: The Classic 20-Minute Test

Test Protocol

Warm-up (20 minutes):
- 10 minutes gradually building to Z2
- 3×1 minute fast pedaling (100+ rpm)
- 5 minutes all-out (to clear anaerobic energy from the legs)
- 5 minutes easy recovery

Main Test:
- 20 minutes all-out, steady riding
- Record the 20-minute average power

Cool-down (10 minutes):
- Gradually decrease intensity

Calculation

FTP = 20-minute average power × 0.95

Why Multiply by 0.95?

This 5% discount comes from empirical observation: most riders’ 20-minute maximum power is approximately 5% higher than their FTP. The 5-minute all-out warm-up serves to deplete some anaerobic energy beforehand, making the 20-minute test closer to a purely aerobic performance.

Advantages

• The most widely accepted method in the industry
• Relatively accurate (error < 5% for most riders)
• The test itself is quality threshold training

Disadvantages

• A 20-minute all-out effort still requires good pacing ability
• The 5% discount varies by individual (the range may be 3-8%)
• Riders with strong anaerobic capacity tend to overestimate FTP
• Mentally grueling, which affects motivation to test

Who Is Likely to Be Overestimated?

If your 1-minute power is very high relative to your FTP (strong anaerobic capacity), you may “borrow” more anaerobic energy during the 20-minute test, making the 0.95 discount insufficient. Your actual discount may need to be 0.92-0.93.

Who Is Likely to Be Underestimated?

Endurance-type riders (with 1-minute power relatively low compared to FTP) may not fully express their aerobic capacity in the 20-minute test because their anaerobic contribution is smaller. These riders may only need a discount of 0.96-0.97.

Method 2: Ramp Test

Test Protocol

Start at a low power and increase by a fixed wattage (usually 20W) every minute,
until you can no longer hold the target power.

Example:
Minute 1: 100W
Minute 2: 120W
Minute 3: 140W
...
Minute 15: 380W
Minute 16: 400W → fails at 16:23

Total test time: approximately 16 minutes

Calculation

FTP = Average power of the final completed minute × 0.75

Or a more precise version:

FTP = Power of the last fully completed minute × 0.75

Different platforms use slightly different calculations:

• TrainerRoad: Best 1-minute power × 0.75
• Zwift: Best 1-minute power × 0.75
• Sufferfest: Uses a more complex multi-point calculation

Why 0.75?

The theoretical basis of the Ramp Test is that when you reach exhaustion during a progressive test, the power in your final minute is approximately equal to your MAP (Maximum Aerobic Power). And FTP is approximately 75% of MAP.

Advantages

• Lowest psychological burden: No pacing required—just hold on until you can’t
• Short duration: Usually over in 15-20 minutes
• High repeatability: Least affected by pacing strategy
• Beginner-friendly: No pacing experience needed

Disadvantages

• The 0.75 varies by individual: The FTP/MAP ratio can range from 0.70 to 0.82
• Biased toward riders with strong anaerobic capacity: If your anaerobic sprint is strong, you can hold on longer in the final stage, causing FTP to be overestimated
• Does not test sustainability: The core of FTP is “sustainability,” but the Ramp Test does not test your ability to sustain power at all

Accuracy Analysis

Research shows the correlation between the Ramp Test and the 20-minute test is approximately r = 0.87-0.93, but individual differences can be large. Some riders see differences exceeding 10% between the two.

Method 3: The 8-Minute Test

Test Protocol

Warm-up (15 minutes):
- 10 minutes Z2
- 3×1 minute fast pedaling
- 2 minutes recovery

Main Test:
- 8 minutes all-out × 2 sets
- 10 minutes recovery between sets

Cool-down (10 minutes)

Calculation

FTP = Higher of the two 8-minute average powers × 0.90

Pros and Cons

Advantages:

• Easier to pace than the 20-minute test
• Two sets provide cross-validation

Disadvantages:

• Slightly less accurate than the 20-minute test
• Greater variability in the 0.90 discount
• Total test time is not much shorter than the 20-minute test

Method 4: Multi-Segment Combination Tests

The Kolie Moore Test (Advanced Recommendation)

Proposed by coach Kolie Moore, this is considered by many to be the most accurate FTP testing method:

Warm-up (15-20 minutes):
- Gradually build intensity

Main Test:
- Start at estimated FTP, ride steadily
- Aim to hold it for as long as possible
- Ideal outcome: naturally fade after 30-60 minutes
- FTP = the maximum power you can hold steadily before fading

Criteria for evaluation:
- If you hold it for > 40 minutes: the power setting is close to your true FTP
- If you hold it for < 25 minutes: the power setting is too high
- If you hold it for > 60 minutes: the power setting is too low

Advantages: Directly tests the definition of FTP—sustained maximum power. No discount factor needed.

Disadvantages: Requires good self-awareness and pacing ability; difficult for beginners to execute.

The 4DP Test (Wahoo SYSTM)

5-second all-out sprint
→ Recovery
→ 5-minute all-out
→ Recovery
→ 20-minute all-out
→ Recovery
→ 1-minute all-out

The advantage is that a single test builds a complete Power Profile; the disadvantage is that the total test time is long and extremely painful.

Method 5: WKO5 Automatic Modeling

Principles

WKO5 uses all your historical riding data to automatically calculate mFTP (modeled FTP) via the Power Duration Model. It does not require you to perform any specific test; instead, it derives the value from your daily training and race data.

Requirements

• Sufficient data volume is needed (at least 8-12 weeks of power data is recommended)
• Near-maximal efforts are needed across different time durations
• If you never do high-intensity rides longer than 5 minutes, mFTP may be inaccurate

Accuracy

With sufficient data, mFTP is surprisingly accurate. Many coaches have completely replaced periodic testing with mFTP.

Accuracy Comparison of Methods

Method	Relative Accuracy	Pacing Requirement	Psychological Difficulty	Test Duration
60-minute all-out	Highest (benchmark)	Extremely high	Extremely high	60+ minutes
Kolie Moore	Very high	High	High	30-50 minutes
20-minute × 0.95	High	Medium-high	High	20 minutes
8-minute × 0.90	Medium-high	Medium	Medium-high	16 minutes
Ramp Test × 0.75	Medium	Low	Medium	15-20 minutes
WKO5 mFTP	High (with sufficient data)	None	None	No test required

Practical Tips for Improving Test Accuracy

1. Standardize Test Conditions

• Same time, same location (ideally a power trainer)
• Similar nutrition and sleep status
• Avoid testing within 48 hours after high-intensity training
• Record temperature and humidity (high heat significantly affects performance)

2. Pacing Strategy

20-minute test:

• First 2 minutes: slightly below target (-5W)
• 2-15 minutes: hold steady at target power
• 15-18 minutes: if it feels manageable, increase slightly
• Final 2 minutes: all-out sprint

Key principle: Better to start slightly conservative and accelerate than to go out too hard and blow up later. The latter will severely underestimate your FTP.

3. Cross-Validation

Don’t rely on just one method. Recommendations:

1. Perform a formal test (20-minute or Ramp)
2. Cross-reference with WKO5 mFTP or Intervals.icu’s eFTP
3. Validate: ride 2×20 minutes at 95-100% of the set FTP—it should feel “hard but sustainable”

If the gap between the three exceeds 5%, you may need to retest or adjust.

4. Testing Frequency

Period	Recommended Frequency
When first starting with a power meter	Every 4 weeks
Stable training period	Every 6-8 weeks
Using WKO5 mFTP	Continuous monitoring; formal test only when anomalies appear

Conclusion

FTP testing should not be something you dread. Choose a method that suits you, stay consistent, and remember: FTP is just a reference point used to calibrate your training zones. A few watts of difference will not affect the quality of your training. What matters is that you have a reasonably accurate and regularly updated FTP value that keeps your training zones in the correct range. Rather than spending too much time chasing the perfect FTP number, spend that time on training itself—after all, the best way to improve your FTP has always been to ride.

Related Reading

• Comprehensive Comparison of FTP Test Methods: Accuracy and Applicability of the 20-Minute Test vs. the Ramp Test
• How to Effectively Improve FTP: From Testing to Practical Training Plans
• The Complete FTP Testing Guide: Comparing the 20-Minute Test, 8-Minute Test, and Ramp Test
• FTP Test Method Comparison: 20-Minute All-Out vs. Ramp Test Accuracy Analysis