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Performance Lab Tool

FTP, Threshold Pace & CSS Calculator

Cycling FTP is 95% of your average power in a 20-minute test. Running threshold pace is the average pace of the final 20 minutes of a 30-minute time trial. Swimming CSS pace per 100 is the difference between your 400 and 200 times divided by two. This tool turns any of those test results into a full, sport-native training-zone table.

Pick your sport, enter your test result, and get your zones instantly. No account required. Share the link with your coach or email yourself a printable zone sheet.

Test protocol
Average power for the test (W)
Body weight (optional, for W/kg)

Your zones update live below as you type.

Not Medical Or Nutrition Advice

This calculator and the resulting plan are educational only. Endurance sports carry inherent risks and individual nutrition needs vary. Athletes should consult a qualified healthcare professional or a registered sports dietitian before applying any nutrition, hydration, or supplementation strategy, especially if you have a medical condition, are pregnant, take medications, or are training through injury. Use this information at your own risk.

Now hold that threshold

Zone 4 is where oxygen economy decides the race

Knowing your threshold is step one. Holding it at a lower oxygen cost is step two. Dietary nitrate improves exercise economy most where it matters: sustained efforts at and just below threshold.

See what a 1 to 2% economy gain saves on your finish time
The Complete Race Day Stack

Sodium Handles Fluid Retention.
Nitrate Handles Oxygen Efficiency.

These are different physiological systems and both matter on race day. Build your sodium strategy with this calculator, then stack Beetroot Pro for the oxygen efficiency layer. The two are additive.

Shop Beetroot Pro®Carb Fueling Plan

Threshold Zones: Common Questions

Threshold is the intensity you can sustain at the edge of steady state. Each sport measures it differently: cycling by FTP (watts), running by threshold pace, and swimming by Critical Swim Speed. Your training zones are then defined relative to that threshold.

How do I calculate FTP from a 20-minute test?

Functional Threshold Power is estimated as 95% of your average power over an all-out 20-minute time trial. If you averaged 260 watts, your FTP is roughly 247 watts. The 8-minute protocol uses 90% of your best effort, and the ramp test uses 75% of your best 1-minute power.

How do I find my running threshold pace?

Run an all-out 30-minute solo time trial on flat terrain. Your threshold pace is the average pace of the final 20 minutes (the first 10 minutes are excluded because you start too fast). That pace anchors your run training zones.

What is CSS and how is it calculated?

Critical Swim Speed is the swimming equivalent of threshold. Swim an all-out 400 and an all-out 200, both timed. CSS pace per 100 equals the difference in the two times divided by two. If your 400 is 6:00 (360s) and your 200 is 2:50 (170s), CSS pace is (360 - 170) / 2 = 95 seconds, or 1:35 per 100.

Why are cycling, running, and swimming zones different?

Each sport uses its own established zone framework. Cycling uses the 7-zone Coggan power model as a percentage of FTP. Running uses Friel functional-threshold-pace zones. Swimming uses CSS-offset bands expressed as seconds per 100. We keep each sport native rather than forcing one system across all three.

How often should I retest my threshold?

Every 4 to 8 weeks during a training block, and after any change in fitness, altitude, or heat acclimation. Threshold rises with training, so zones built on a stale test gradually become too easy. Retest, then regenerate your zones.