“Too much, too fast” is the most common explanation for overtraining symptoms—and the vaguest. What “too much” means depends on what came before. The Session RPE method turns this into a number that can be calculated without lactate testing or a power meter: effort times duration. The calculator uses this to determine your weekly load, checks how consistent the week was, and compares it to previous weeks.
Effort times Duration
The method was developed by Carl Foster and is strikingly simple: About half an hour after your workout, you rate the effort of the entire session on a scale from 1 to 10. You then multiply this value by the duration in minutes.
One hour of moderate training at an RPE of 5 equals 300. Thirty minutes of hard training at an RPE of 9 equals 270—almost the same, even though the sessions feel completely different. That’s exactly the point: the number makes it possible to compare volume and intensity.
The difference of about thirty minutes is not a minor detail. Immediately after the last repetition, the end of the session dominates the assessment; later, this evens out. And the question is “how strenuous was the session overall,” not “how exhausted am I right now.”
Monotony: the underestimated factor
Two weeks can have the same total load and still feel completely different. Three hard days with four days off is different from seven days of moderate training.
Monotony captures exactly that: the average daily load divided by its variation across the seven days. Those who do roughly the same amount every day end up with a high score; those who alternate between hard days and true rest days end up with a low score. As a rule of thumb, a value above 2 is a warning sign—Foster observed in his work that infections and ailments occurred more frequently after weeks with high monotony and high total load.
Combining these two factors yields “strain”: weekly load multiplied by monotony. It rises particularly when an already strenuous week contains no days of rest.
The Relationship to Previous Weeks—With Reservations
The best-known metric in this field is the ratio of current to previous workload, usually referred to as the Acute-Chronic Workload Ratio. The idea: A week that is far above the previous average places a strain on a body that is not prepared for it. A range of 0.8 to 1.3 is generally considered safe, while anything above 1.5 is considered a danger zone.
These figures are more widely known than the available data warrants. Several methodological studies have dissected the original formula: In the classic calculation, the current week is also included in the denominator, which creates a spurious mathematical correlation; the threshold values are derived from just a few small studies; and the apparent link to injuries disappears when the most extreme data points are removed.
That is why this calculator uses the decoupled version: The current week is in the numerator, while the denominator consists exclusively of the preceding weeks. This is the formula that even critics cite as a more sensible alternative. And the range from 0.8 to 1.3 is provided here as a planning aid, not as an injury threshold.
The number remains practically useful nonetheless—but simply for what it is: a description of how much this week deviates from the norm.
What the Numbers Don’t Know
The Session RPE treats all types of exertion as equal. An hour of endurance running and an hour of maximum strength training yield the same value even though they demand effort from completely different parts of the body and have lingering effects of varying durations. Eccentric exercise, jumps, and downhill running are significantly underrepresented in the figure.
Nor does the calculation take into account sleep, stress, and nutrition—and these factors often play a bigger role in how well you cope with a week than the training load itself. That’s why it’s worth checking the HRV interpreter and the sleep needs calculator as well.
And the RPE assessment itself varies. It’s surprisingly reliable for trained athletes, but often inconsistent for beginners—they simply don’t know the difference between a 6 and an 8 yet. That doesn’t make the method worthless, but it does require a few weeks of adjustment before the numbers become meaningful.
How to Plan With It
The benefit lies less in evaluating the past week than in planning the next one. The calculator therefore directly displays the range within which the coming week would fall if you stay within the corridor.
A proven approach is to build up the intensity over three to four weeks and then significantly reduce it for one week—to about half to two-thirds of the previous level. This recovery week appears in the calculator as a ratio well below 0.8, and that’s exactly the intended effect.
Those who return to training after a break face the opposite problem: their chronic load is low, so every normal week appears as a large jump in the calculation. Here, the number is only of limited help; it makes more sense to deliberately stay below what you feel you can handle for the first two to three weeks.
For gyms: low barrier to entry, high impact
Session RPE is the only method of training control that requires no technology whatsoever. A single number after each session, jotted down in any list—that’s all it takes. This makes it appealing for gyms that don’t use power meters or heart rate monitors across the board.
When it comes to coaching, comparing data over several weeks is particularly helpful. Members who complain of discomfort have, surprisingly often, just had a week with an increase of more than fifty percent—and that only becomes apparent when someone compares the numbers side by side.
For classes, the predictability is also beneficial: Someone who attends the same class three times a week at the same intensity will, mathematically speaking, have a very consistent week. A suggestion for a deliberate rest day or a less intense alternative then becomes a concrete piece of advice rather than a general recommendation.
Frequently Asked Questions / FAQ
What is the unit of measurement for training load?
It has no physical unit. The value is an arbitrary number that only makes sense when compared to your own previous weeks. Comparing two people isn’t meaningful.
Does everyday movement count?
Not in the classic method—it tracks planned training sessions. People who do physical labor or commute a lot have a correspondingly higher baseline activity level that isn’t reflected in the number. For such professions, it’s worth interpreting the thresholds a bit more conservatively.
What should I do on days with two sessions?
Add both together for the weekly load. For the sake of consistency, they should be combined into a single day; otherwise, the week will be calculated as more uniform than it actually was.
Is a ratio above 1.5 dangerous?
The data isn’t that clear-cut. The threshold is based on only a few studies and has been heavily criticized in the scientific literature. Still, it serves as a good indicator that a week is significantly out of the norm.
How long do I need to keep track of my data before the numbers become meaningful?
Two to three previous weeks are sufficient for a ratio. For a reliable picture of your own patterns, eight to twelve weeks is realistic—then you’ll also see which weekly structure actually works best for you.
Editorial Team, fitnessmarkt.de
Image source: #11892962 karlyukav / freepik.com
Published on: 14 January 2026