The ACWR calculator tells you whether your training this week has jumped too far ahead of what your body is used to — the single most useful early-warning signal for overuse injury. This guide walks through using it from scratch. If you want the science behind the number first, thefull ACWR guide covers that.

What you need before you start

Almost nothing. Specifically:

A rough memory of how long you trained each of the last 7 days (in minutes).
A sense of how hard each session felt — easy, moderate, hard, or very hard.
A rough idea of what a normal training week looks like for you (days per week, typical session length, usual effort).

You do not need a wearable, a heart-rate strap, or any load numbers you've tracked before. The calculator does the math for you.

Step 1 — Fill in your last 7 days

Each row is one day. Enter the minutes you trained and pick the effort that matches how the session felt. The calculator instantly multiplies them into a training-load number (shown on the right of each row) — this is the standard "session-RPE" method sports scientists use, where load = effort × duration.

Rest day? Leave it at 0 minutes / Rest. It counts as zero — you don't skip it.
Two sessions in one day? Add the minutes together and pick the effort of the harder one. It's an estimate, not a lab measurement, so close is fine.
Which effort? Easy is a conversational recovery pace. Moderate is steady work you could sustain. Hard is a quality session you're glad to finish. Very hard is a near-maximal or race-type effort.

The page loads with an example week already filled in so you can see how it behaves — just type over it with your own numbers.

Step 2 — Describe a normal week

This is the part most ACWR calculators get wrong: they demand a "chronic load" figure nobody has tracked. Instead, this one estimates your baseline from three simple questions — how many days a week you usually train, a typical session length, and your usual effort. That's enough to approximate the 4-week rolling average your acute week is compared against.

If your training is very consistent, this estimate will be close. If it swings a lot week to week, use a genuinelyaverage week rather than your best or worst one.

Step 3 — Read your ratio

The result updates live as you type. The big number is your acute-to-chronic workload ratio (ACWR): this week's average daily load divided by your baseline daily load. It lands in one of three zones:

0.8–1.3 — Sweet spot. This week is close to what your body is adapted to. Associated with the lowest injury risk.
1.3–1.5 — Caution. You've ramped faster than your base. Manageable, but don't stack another jump on top this week.
Above 1.5 — Danger zone. A load spike well beyond your base — where injury-risk research shows the sharpest increase. Consider backing off.
Below 0.8. Not dangerous like a spike, but a sustained low ratio usually means fitness is fading — fine for a taper or deliberate easy week, not as a permanent state.

How to read the result honestly

ACWR is a signal, not a verdict. A few things worth keeping in mind:

One reading is a snapshot. The trend across several weeks matters more than any single number. Check it regularly rather than obsessing over one day.
It's an estimate. Effort ratings are subjective and the baseline is approximated, so treat the ratio as a rough guide, not a precise measurement.
It's not medical advice. A "sweet spot" number doesn't guarantee you won't get hurt, and a high one doesn't mean you will. It's one input among many, including how you actually feel, sleep, and recover.

Common questions

What's a good ACWR?

Roughly 0.8 to 1.3. That range is repeatedly associated with the lowest injury risk in training-load research. Seethe full ACWR guide for where those thresholds come from and their limits.

I don't know my exact minutes — does it matter?

Not much. ACWR is about relative change, not precision to the minute. Reasonable estimates that you apply consistently week to week will give you a useful trend.

How often should I check it?

Once a week is plenty for most people — for example, every Sunday looking back at the week just finished. What you're watching for is a sharp jump, not daily wobble.

Does this replace what the app does?

No. This calculator is a manual, one-week snapshot. Mass in Motion tracks your load automatically every day using an exponentially weighted average, keeps running and lifting on separate streams, and folds ACWR into a widerdaily recovery score that adjusts your training — rather than asking you to fill in a form.

Try it

That's the whole method. Open the ACWR calculator, type in your week, and read your ratio. Then, if the number surprised you, the ACWR guide explains what to do about a spike — and how Mass in Motion manages it for you across lifting and running.

How to Use the ACWR Calculator