Use General, Cardio, or Strength to match the workout you are reviewing.
Use Borg 6-20, CR10 0-10, or Strength 1-10 exactly as logged.
{{ displayRPE }}
Use the selected scale range; Borg steps by 1, CR10 and Strength by 0.1.
RPE
Choose Custom to keep manual entries, or a named effort to quick-fill scale and RPE.
Select None, Estimate from age, or Use known max HR; this only affects HR output.
Enter whole years from 10 to 100, e.g. 42.
years
Available equations: Tanaka, Fox, or Gulati.
Enter 100-240 bpm; leave blank if you do not know your max HR.
bpm
Enter 30-120 bpm and keep it lower than max HR.
bpm
Enter 0-600 minutes; any value above 0 enables sRPE load outputs.
min
Use Linear for the standard crosswalk; bias modes curve low or high effort response.
Section Field Value Detail Copy
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Perceived exertion is subjective. Use the crosswalk as a coaching cue, not as a medical test or an exact substitute for measured performance data.
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Felt effort matters when a workout cannot be judged by speed, watts, weight on the bar, or heart rate alone. A humid run at the same pace can feel harder than last week, a lifting set can be limited by fatigue before the programmed load looks heavy, and medication or illness can make heart-rate zones less reliable. Rate of perceived exertion, usually shortened to RPE, gives that internal strain a number.

RPE is not one single scale. The classic Borg scale runs from 6 to 20 and is common in exercise testing, rehabilitation, and endurance settings. The CR10 scale uses 0 to 10 and is common for breathlessness, exertion, and session-RPE training load. Strength training often uses a 1 to 10 lifting RPE tied to repetitions in reserve, where a near-10 set means almost no reps are left before failure. The numbers look similar in places, but they do not mean the same thing until the scale is named.

Perceived exertion signals mapped across Borg, CR10, strength RPE, and sRPE load

The useful part of RPE is that it combines signals a watch or training log may split apart: breathing, leg heaviness, muscle fatigue, coordination, pain, confidence, heat, sleep, stress, and the sense that another minute or another rep would be costly. That also makes it easy to misread. A high number can mean a hard session, poor recovery, unfamiliar terrain, poor pacing, or a set taken close to failure. A low number can mean the workout was truly easy, but it can also mean the athlete is skilled, rested, or underreporting effort.

RPE works best when it is compared with context rather than treated as a medical measurement. Endurance athletes often pair it with pace, power, heart rate, and the talk test. Lifters compare it with load, reps, bar speed, and repetitions in reserve. Coaches often multiply a CR10-style session rating by minutes to estimate internal training load. Across all of those uses, the main discipline is consistency: use the same scale, ask the question at a similar time, and avoid comparing a lifting-set RPE directly with a whole-run RPE without translating the scale first.

Because RPE is self-reported, it should guide training review rather than diagnose fitness, heart health, pain, or readiness to exercise. New exercisers, highly trained athletes, people taking heart-rate-changing medication, and anyone exercising in heat or during illness may need extra caution when turning a felt number into a training decision.

How to Use This Tool:

Start with the scale and context that match the workout log. The calculator updates immediately as you move the slider or change the advanced fields.

  1. Choose Effort context as General conditioning, Cardio / endurance, or Strength / lifting. This changes the recommendation wording while keeping the same numeric crosswalk.
  2. Set Scale to the rating language you used: Borg 6-20, CR10 (0-10), or Strength 1-10. Use Borg for whole-number 6 to 20 entries, CR10 for 0 to 10 exertion, and Strength 1-10 for lifting-style set ratings.
  3. Enter RPE value with the slider or number field. Borg rounds to whole steps; CR10 and Strength allow decimal steps, which helps with values such as 6.5 or 8.5.
  4. Use Preset only when you want a starting point such as Recovery effort, Steady cardio, Threshold cardio, Working sets, or Near max lift. After the preset loads, adjust the value if the actual session felt different.
  5. Open Advanced when you want optional heart-rate or load context. HR estimate basis can use age formulas or a known max HR, Resting HR switches the cue to heart-rate reserve when it is valid, and Session length turns the CR10 equivalent into Session load (sRPE).
  6. Leave Mapping on Linear for the clearest scale comparison. Use Mild bias or Hard bias only when you deliberately want the response curve to reshape lower and higher effort values.
  7. Read any warning above the result tabs before using the numbers. Age outside 10 to 100, max HR outside 100 to 240 bpm, resting HR at or above max HR, or a cardio-strength cross-context translation should be corrected or treated as approximate.

Interpreting Results:

Normalized intensity (%) is the main comparison value. It puts Borg, CR10, and Strength 1-10 entries onto one 0% to 100% effort position, then the calculator reads that same position back as Equivalent CR10, Equivalent Borg, and Strength-equivalent RPE.

Intensity band and Talk test cue are practical checks, not proof that the workout was good or bad. A high band does not confirm improved fitness, and a low band does not mean the session was wasted. Compare the result with pace, power, load, reps, symptoms, recovery, and whether the selected scale matches the activity.

Normalized intensity Band Talk-test cue Useful first read
<= 35% Recovery Full sentences Warm-up, cooldown, recovery movement, or low-stress skill work.
> 35% to 55% Easy Easy conversation Comfortable aerobic volume or easy strength volume with reserve.
> 55% to 70% Steady Short sentences Controlled work that should still allow planned duration or technique.
> 70% to 85% Hard Short phrases Focused work where fatigue and next-session timing matter.
> 85% to 95% Very hard Single words Short intervals, surges, top sets, or near-limit efforts.
> 95% to 100% Maximal No talking Limit effort rather than normal repeatable training.

Use Effort Gauge for a quick band check, Response Curve to see how the mapping setting changes the current scale, and sRPE Load Ladder to see how the same felt effort becomes a larger load as minutes increase.

Technical Details:

Scale conversion starts by turning the entered RPE into a fraction from 0 to 1. Borg uses the distance between 6 and 20, CR10 uses the distance between 0 and 10, and the strength scale uses the distance between 1 and 10. That shared fraction is why a CR10 value, a Borg value, and a lifting RPE can be compared without pretending the original scales have identical anchors.

The optional mapping setting reshapes the fraction after the scale conversion. Linear mapping leaves the fraction unchanged. Mild bias raises most non-zero submaximal values by applying a 0.85 exponent. Hard bias lowers most submaximal values by applying a 1.2 exponent, so the upper end rises later. Values are clamped to the selected scale range before conversion.

Formula Core:

The formulas below show the main crosswalk. Let x be the entered RPE after range clamping and let f be the mapped effort fraction.

fraw = (x-6)/14 for Borg 6-20 fraw = x/10 for CR10 fraw = (x-1)/9 for Strength 1-10 f = fraw, fraw0.85, or fraw1.2 I = f×100 RPEstrength = 1+f×9 RIR = max(0,10-RPEstrength)

With CR10 set to 7.0 and linear mapping, f is 0.70. The resulting Normalized intensity (%) is 70%, Equivalent Borg is 15.8, Strength-equivalent RPE is 7.3, and the strength reserve cue is about 2.7 RIR.

Heart-Rate and Load Estimates:

Heart-rate cues use the same effort fraction. A known max HR can be entered directly, or age can estimate max HR with Tanaka, Fox, or Gulati. If a valid resting HR is present and lower than max HR, the estimate uses heart-rate reserve; otherwise it uses a straight fraction of max HR.

HRmax = 208-0.7×age, Tanaka HRmax = 220-age, Fox HRmax = 206-0.88×age, Gulati HRestimate = HRrest+f×(HRmax-HRrest) sRPE = Equivalent CR10×session minutes
Item Boundary Effect
Age 10 to 100 years Needed for age-based HRmax formulas.
Max HR 100 to 240 bpm Bypasses age formulas when a known maximum is available.
Resting HR 30 to 120 bpm and below max HR Uses heart-rate reserve instead of percent of max HR.
Session length 0 to 600 minutes Enables session-RPE load when greater than 0.
Load bands Light < 150, Moderate 150 to < 300, Hard 300 to < 450, Very Hard >= 450 Classifies CR10-equivalent effort multiplied by minutes.

The heart-rate estimate is only a cue. Age formulas can be wrong for an individual, and a felt effort fraction is not the same as a measured lab threshold, ventilatory threshold, lactate threshold, one-repetition maximum, or clinical stress-test result.

Limitations:

RPE is an informational training estimate. It should not replace medical advice, supervised rehabilitation guidance, measured performance testing, or a safety plan for painful or unusual symptoms.

  • Compare sessions only when the scale, context, mapping, and timing of the rating are reasonably consistent.
  • Treat cardio-to-strength or strength-to-cardio translations as rough crosswalks, especially near maximal effort.
  • Use measured heart rate, pace, power, load, reps, and recovery notes when a training decision needs more than a self-reported number.
  • Stop and seek appropriate guidance if exertion comes with chest pain, faintness, unusual shortness of breath, or symptoms that do not match the planned workout.

Advanced Tips:

  • Keep Mapping on Linear when you need the cleanest Borg, CR10, and Strength 1-10 comparison; record any bias mode if you compare the same session later.
  • Use Session length when the session was long enough for load to matter. A moderate CR10 value can still produce a high Session load (sRPE) when the duration is large.
  • Prefer a tested Max HR and a valid Resting HR when heart-rate cues matter. Age formulas are broad estimates and can miss individual maximum heart rate by a large margin.
  • Read Strength-equivalent RIR as a lifting-effort cue, not as a fixed percent of one-repetition maximum. Reps performed, exercise choice, technique, and bar speed still matter.
  • Use Response Curve before changing the mapping mode for a training block, and use sRPE Load Ladder when you need to explain why the same felt effort creates more load as minutes increase.

Worked Examples:

Steady run with session load

A steady run logged as CR10 5.0 with Linear mapping gives Normalized intensity (%) of 50%, an Easy Intensity band, Equivalent Borg of 13.0, and an easy-conversation Talk test cue. If Session length is 60 minutes, Session load (sRPE) is 300, which enters the Hard load band even though the intensity itself remains Easy.

Borg threshold entry

A threshold-style cardio session logged as Borg 15 converts to about 64.3% Normalized intensity (%) and 6.4 Equivalent CR10 with linear mapping. The band is Steady, while the Borg descriptor still reads hard. That difference is a reminder to read the original scale label and the normalized crosswalk together.

Near-limit lifting set

A lifting top set entered as Strength 9.5 gives about 94.4% Normalized intensity (%), a Very hard band, and roughly 0.5 Strength-equivalent RIR. If Effort context is set to cardio, the warning about translating the Strength 1-10 scale tells you to treat the talk-test cue as approximate rather than as a precise endurance prescription.

Heart-rate warning recovery

If the warning says the heart-rate cue is off, check the advanced fields first. An age of 8, a max HR of 260 bpm, or a resting HR equal to max HR will prevent or weaken Estimated HR (bpm); correcting those values restores the cue when the rest of the setup is valid.

FAQ:

Which RPE scale should I choose?

Choose the scale used in your workout log, coach note, app, or program. Do not enter a lifting RPE as CR10 just because both have 10 at the top.

Why does the strength result show RIR?

Strength-equivalent RIR is calculated from the strength RPE crosswalk as about 10 - Strength-equivalent RPE. It is a reserve cue, not a fixed percent of one-repetition maximum.

Does session load change the intensity band?

No. Intensity band comes from the RPE value and mapping. Session load (sRPE) multiplies the CR10 equivalent by minutes, so a longer session can have a higher load without a higher intensity band.

Why did the heart-rate estimate disappear?

The warning area names the problem. Age must be 10 to 100 years, known max HR must be 100 to 240 bpm, and resting HR must be 30 to 120 bpm and lower than max HR to use heart-rate reserve.

Is the estimated heart rate a target zone?

Treat Estimated HR (bpm) as a rough cue for the entered effort, not a prescribed target zone. Use your measured heart rate and professional guidance when heart-rate limits matter for safety.

Glossary:

RPE
A self-reported rating of how hard exercise feels.
Borg 6-20
A classic perceived-exertion scale often used in exercise testing and endurance contexts.
CR10
A 0 to 10 category-ratio style effort scale used for exertion and session-RPE load.
RIR
Repetitions in reserve, or the estimated number of reps left before a lifting set reaches failure.
sRPE
Session-RPE load, calculated here as equivalent CR10 multiplied by session minutes.
Heart-rate reserve
The range between resting heart rate and maximum heart rate.

References: