What is ACWR and why does it matter?

The acute:chronic workload ratio compares this week's training load to your rolling average. Research by Tim Gabbett and others shows that ACWR above 1.5 is associated with a 2–3× increase in injury probability across multiple sports. It's the most actionable load metric available to athletes without lab testing.

What is RPE and how do I measure it?

RPE (Rate of Perceived Exertion) is a 1–10 scale of exercise intensity. 1–2 is very easy recovery pace. 5–6 is moderate, conversational effort. 7–8 is hard but sustainable. 9–10 is maximal effort. Use the Borg CR-10 scale: if you could hold a full conversation, you're at 3–4. If you can say a sentence between breaths, you're at 6–7. If you can't speak, you're at 9+.

What is TSS (Training Stress Score)?

TSS is a composite load metric that accounts for both duration and intensity. In this calculator, TSS is estimated using the session RPE method: TSS = duration(min) × RPE² / 100. A 60-minute run at RPE 6 scores 21.6 TSS. A 45-minute threshold run at RPE 8 scores 28.8 TSS. The session RPE method correlates well with power-meter TSS for most athletes.

How much can I increase training load each week?

The traditional guideline is the 10% rule — no more than 10% weekly volume increase. Research on ACWR suggests a more nuanced approach: keep your ACWR below 1.3, especially if you have low chronic fitness. Fitter athletes with high chronic loads can tolerate larger absolute increases while staying within safe ACWR ratios.

Is zero rest days ever acceptable?

No. Even elite athletes build rest or active recovery days into every training week. Zero rest days prevents tissue repair, disrupts hormonal recovery, and doesn't allow the nervous system to consolidate adaptations. Active recovery (walking, light yoga, swimming at RPE 1–2) does not count as a rest day in the traditional sense but provides physiological benefit.

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Training Load Calculator — Is Your Workload in the Safe Zone?

Is your training load in the safe zone this week?

What This Does

The acute:chronic workload ratio (ACWR) is the most evidence-based metric in sports science for predicting injury risk. It compares your current week's training load (acute load) to your rolling average over the past 4–6 weeks (chronic load). The ratio tells you how much harder or easier you are training relative to what your body has adapted to. The sweet spot is an ACWR between 0.8 and 1.3. Below 0.8 means you're undertrained and not providing enough stimulus to maintain fitness. Above 1.3 means you've spiked your training load faster than your body can adapt — injury risk climbs sharply. Above 1.5, research shows a two- to three-fold increase in injury probability. This calculator uses RPE-based session load (duration × RPE²/100) — a validated proxy for training stress that works for any sport without requiring power meters or GPS. Log each session by duration, rate of perceived exertion, and type. The calculator outputs your ACWR, weekly TSS, overall load score, and prioritized recommendations for the coming week. Whether you're a runner building marathon base, a CrossFit athlete managing volume, or a team sport player in-season, this tool makes load monitoring accessible without a sports scientist.

When Should You Use This?

→Planning your training week and deciding how hard to push
→Returning from injury or illness and gradually rebuilding volume
→Feeling unusually fatigued or sore and wanting to know if it's overload
→Following a new program and checking if the ramp rate is safe
→Preparing for a competition or race and managing peaking
→Coaching athletes and monitoring team training load

Example Scenario

Marcus, a 34-year-old competitive runner, logged 6 training sessions this week: two easy 45-min runs (RPE 4), one 60-min threshold run (RPE 8), one 30-min easy run (RPE 4), and a 90-min long run (RPE 6). His previous week's load was 280 TSS. The calculator shows his ACWR at 1.38 — in the caution zone. His recommendation: reduce volume by 20% next week and add a rest day before the next threshold session.

Training Load Calculator

What Is My Training Load? — ACWR Analysis

Log this week's sessions (duration + RPE) to calculate your Acute:Chronic Workload Ratio, injury risk, and optimal next-week target. Results update live as you type.