ExRx 1RM Calculator vs MaxRep: Formula Result or Training Workflow?
ExRx and MaxRep can both turn a submaximal set into a one-rep max estimate. The useful difference is the workflow around the result, not a claim that one calculator can know your true max from two inputs.
What the two tools have in common
Both start with weight and completed reps. Both produce a prediction based on a mathematical relationship between repetitions and load. Neither can observe range of motion, exercise variation, fatigue, or how many reps remained.
The official ExRx 1RM calculator is a direct option inside ExRx’s larger exercise and testing reference. MaxRep is designed around comparing estimates and continuing into other strength tools.
The practical differences
| Need | ExRx | MaxRep |
|---|---|---|
| Quick 1RM estimate | Yes | Yes |
| Compare several formulas in one result | Check the current ExRx interface | Seven estimates and a visible range |
| Separate squat, bench, and deadlift entry pages | Exercise reference pages are available | Yes |
| RPE-aware estimate | Check the current ExRx tools | Dedicated RPE 1RM calculator |
| 5x5 working-weight estimate | Check the current ExRx tools | Dedicated 5x5 calculator |
| Continue to video velocity analysis | No integrated MaxRep workflow | Power VBT links the next step |
This table avoids assigning accuracy percentages to either product. A calculator cannot validate itself by displaying a precise error number.
Compare the same set before choosing
Enter the same recent set in both tools. If the answers differ, identify the formula and assumption before deciding which number to use. Lower-rep, near-limit sets usually provide a cleaner input than high-rep sets, but exercise and individual fatigue patterns still matter.
MaxRep’s main 1RM page shows a reference range from multiple formulas. That makes disagreement visible and encourages a conservative training baseline. The RM calculator then converts the chosen baseline into working weights.
Where video changes the question
Rep calculators ask how load and completed reps relate. VBT asks how load and movement velocity relate for this lifter. Power VBT analyzes a recorded set, shows mean concentric velocity and bar path for each rep, and can build a load-velocity profile. Research supports the value of velocity monitoring while also finding uncertainty in 1RM extrapolation, so the result should remain a training estimate.
Use MaxRep’s 1RM calculator for a fast formula comparison. Use Power VBT on iPhone or Android when you want a record built from the movement itself.