Skip to content

Cardio RPE Calculator

Map your cardio effort to training zones using Borg or Tuchscherer scales

Calculation Mode

Activity

Duration recommendations are adjusted per activity

Borg 6-20 Scale

6 8 10 12 14 16 18 20
Borg

6 = no exertion at rest, 20 = maximal effort

The original Borg scale was designed so the rating multiplied by 10 approximates heart rate. Borg 15 corresponds to roughly 150 bpm for a typical adult.

RPE 6-10 Scale

6 7 8 9 10
RPE

Originally used for strength training, adapted here for sustained cardio effort

RPE 10 = absolute maximum effort. RPE 6 = very light movement, easy conversation. Half-point increments allow fine-tuning between effort levels.

Heart Rate Inputs

bpm

Use 220 minus age as a starting estimate

bpm

Your measured or target heart rate during exercise

Current HR cannot exceed Max HR. Please check your values.

Current effort: of max heart rate

Training Zone

HR Range

Intensity

Borg Equivalent

Recommended Session Duration

For at Zone

Recommended Duration

Primary Training Effect

Full Zone Reference

All five zones with Borg, RPE 6-10, and duration guidelines for

Zone Name % MHR Borg RPE 6-10 Duration

Borg Scale Cross-Reference

Full Borg 6-20 scale mapped to RPE 6-10 equivalents and training zones

Borg Descriptor RPE 6-10 Zone

Related Calculators

RPE Chart Full Tuchscherer percentage reference E1RM Calculator Estimate your one-rep max from any set Volume Landmarks Track weekly volume vs MEV, MAV, MRV

Understanding Cardio RPE and Training Zones

Cardio RPE (Rate of Perceived Exertion) gives you a reliable, low-tech way to measure exercise intensity without a heart rate monitor. Two scales dominate the field: the classic Borg 6-20 scale and the strength-training-derived Tuchscherer RPE 6-10 scale. Understanding both - and how they map to heart rate zones - helps you train smarter across any aerobic activity.

The Borg 6-20 Scale

Developed by Swedish psychologist Gunnar Borg in the 1970s, the original RPE scale runs from 6 (complete rest) to 20 (absolute maximum exertion). The range was deliberately chosen so that multiplying the rating by 10 approximates heart rate in beats per minute for a healthy young adult. A rating of 13 ("somewhat hard") corresponds to roughly 130 bpm. This makes the scale an indirect but surprisingly accurate proxy for cardiovascular intensity - no chest strap required. The Borg scale is used worldwide in clinical cardiac rehab, VO2 max testing, and endurance sports coaching.

Tuchscherer RPE Adapted for Cardio

Mike Tuchscherer's RPE 6-10 scale was originally created for powerlifting, where it quantifies how many reps remain in reserve on a strength set. For cardio purposes, the same 6-10 spectrum maps cleanly to sustained effort levels: RPE 6 is light conversational movement, RPE 8 is comfortably hard tempo pace, and RPE 10 is an all-out sprint or race effort. Because the scale is compressed into five points with half-point increments, it offers fine-tuning without the cognitive overhead of a 15-point scale - useful for athletes who already use RPE in their strength training.

Heart Rate Zones and Their Training Effects

The standard 5-zone model divides the space between 50% and 100% of maximum heart rate into five bands. Zone 1 (50-60% MHR) supports active recovery and fat oxidation at very low intensity. Zone 2 (60-70%) builds the aerobic base that underpins all endurance performance - most elite athletes spend 70-80% of training volume here. Zone 3 (70-80%) develops tempo fitness and aerobic capacity at a comfortably hard pace. Zone 4 (80-90%) pushes the lactate threshold, raising the ceiling of sustainable hard effort. Zone 5 (90-100%) targets VO2max and anaerobic capacity through short, intense intervals.

Why Activity-Specific Duration Recommendations Matter

Running, cycling, rowing, and swimming impose different mechanical and cardiovascular demands at the same heart rate. Running carries high repetitive impact stress on joints, so Zone 4 sessions are typically capped shorter than equivalent cycling efforts. Rowing and swimming engage the upper body heavily, increasing local muscular fatigue relative to heart rate. This calculator accounts for those differences and provides activity-specific duration targets that reflect the actual training stress - not a generic one-size-fits-all figure.

Frequently Asked Questions

The Borg 6-20 scale was designed specifically for cardiovascular exercise. Its 15-point range allows fine discrimination between effort levels, and the numbers were chosen so that rating x 10 approximates heart rate in bpm. The Tuchscherer RPE 6-10 scale was originally created for powerlifting to count reps in reserve, then adapted for endurance work. It uses a compressed 5-point range with half-point increments. Both scales measure perceived exertion - the Borg scale gives more granularity across the full cardio spectrum, while RPE 6-10 is more familiar to athletes who also strength train.
The most common formula is 220 minus your age. For example, a 35-year-old would estimate 220 - 35 = 185 bpm. This is a population average with a standard deviation of about 10-12 bpm, so it can be off by 10-20 bpm for any individual. More accurate methods include a graded exercise test supervised by a sports medicine professional, or a field test such as a hard 3-5 minute all-out effort after a thorough warm-up. For training purposes, the 220-minus-age formula is a reasonable starting point - adjust if your perceived zones do not match the expected effort levels.
Yes - RPE is a validated and widely used tool in exercise science. Research consistently shows that trained individuals can regulate intensity accurately using RPE alone, achieving heart rates within 5-10 bpm of target. The advantage of RPE is that it accounts for factors a heart rate monitor cannot: daily fatigue, heat, humidity, altitude, caffeine, and mental stress all affect how hard an effort feels relative to the heart rate it produces. For recreational and intermediate athletes, RPE is often more practical and just as effective as heart rate monitoring for pacing workouts.
Zone 2 (60-70% of max heart rate, Borg 9-11, RPE 6.5-7) is the aerobic base zone where fat oxidation is maximized and mitochondrial density increases with consistent training. It is popular because it produces significant cardiovascular adaptations with minimal recovery cost - you can train Zone 2 frequently without accumulating excessive fatigue. Elite endurance athletes spend 70-80% of their training volume in Zone 2. Sessions should feel comfortably conversational - you should be able to speak in full sentences throughout.
Use the talk test as a simple guide. Zone 1-2: you can hold a full conversation without pausing for breath. Zone 3: you can speak in short sentences but not comfortably chat continuously. Zone 4: you can only manage a few words at a time. Zone 5: speaking is not possible. Cross-reference with the Borg scale: if your effort feels like Borg 12-14, you are likely in Zone 3. Borg 15-17 indicates Zone 4. With practice, most people can estimate their zone within one level using perceived exertion alone.

Zone boundaries and duration recommendations are population-level guidelines. Individual heart rate response, fitness level, and environmental conditions all affect the appropriate intensity for a given session. Consult a physician before beginning a new exercise program.