When the One Rep Max Calculator seems to misbehave, the cause is usually one of two things: something stopped the tool from running, or it ran but the result is not usable. This guide starts with the fastest checks, then walks through the common problems and exact fixes.
Quick Checks First
- Refresh the page - a stalled session is the most common cause of nothing happening.
- Confirm the input is not empty and actually contains what you meant to submit.
- Try the smallest possible input; if that works, the issue is size, not the tool.
- Turn off browser extensions that block scripts, then reload and test again.
- Update or switch browsers if the problem repeats across sessions.
Common Problems and How to Fix Them
The estimate feels too optimistic.
Epley runs optimistic for higher rep sets - use rep counts of one to five for the most trustworthy numbers.
The estimate feels too low.
Deep technique and full range lifts often undersell raw gym numbers - consistency across attempts matters more.
My real max attempt came in under the estimate.
That is normal - treat the formula as a planning ceiling and test conservatively with a spotter.
The percentage table jumps oddly.
Percentages derive from the single estimate - small input changes shift the whole table proportionally.
I cannot decide which lift to enter.
Run each lift separately - squat, bench and deadlift all have their own ratios and rep relationships.
Is this safe to max with?
No - estimates reduce the need to test; if you do test, use proper warm-ups, spotters and coaching.
When It Works but the Output Is Poor
If the tool runs fine but the result misses, the problem is almost always the brief, not the software:
- Treating the estimate as a tested max
- Grinding shaky reps for a better number
- Mixing formulas between attempts
- Programming too close to the estimate
How to Stop It Happening Next Time
- Keep a saved prompt template for every task you repeat.
- Change one setting per generation so causes stay obvious.
- Run a two-minute sanity test with known input after any update.
- Note every failure and its fix; a short troubleshooting log pays for itself.
Still Stuck?
Reproduce the problem with the smallest possible input and note the exact steps that triggered it. A one-line description of what you did, what you expected and what happened is enough to get a precise answer from support or a colleague.
Frequently Asked Questions
Which formula does it use?
The Epley formula - weight multiplied by one plus reps divided by thirty - one of the most common estimates.
How accurate is the estimate?
Closest for low rep sets within a few percent; higher rep sets drift, so plan conservatively.
What reps should I enter?
Sets of one to five give the best estimates; very high rep sets overstate true single strength.
Is my lift data stored?
No - everything stays in your browser.
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