Estimated strength and loadable percentages
The primary result uses the selected formula; both predictions remain visible for comparison. The formula difference is not an error bound. Percentage loads use the unrounded selected estimate and are then rounded down to a whole number of the entered total-load increment. For one completed rep, the tool reports the weight actually lifted.
To convert your lifted weight or total-load increment between kilograms and pounds, use the Weight Converter before changing the unit here.
The formula
w is the total load lifted and r is the completed repetition count. This calculator accepts 1–10 repetitions and uses the common unrounded r/30 Epley form; some references show its coefficient rounded to 0.033. Percentage load = selected estimate × percentage / 100. Rounded-down load = increment × floor(percentage load / increment). Both formulas preserve the input weight unit.
100 kg lifted for five repetitions
For 100 kg and five completed reps, Epley estimates 100 × (1 + 5/30) = 116.67 kg. Brzycki estimates 100 × 36/32 = 112.50 kg. With Epley selected, the 80% load is 93.33 kg before display rounding; at 2.5 kg total-load increments, the loadable value is rounded down to 92.5 kg.
How to use this calculator
- Enter the total external weight lifted in a completed set, including the bar where applicable.
- Choose kilograms or pounds and enter a whole-number repetition count from 1 to 10.
- Select Epley or Brzycki as the primary prediction and enter the smallest total-load increment available.
- Calculate, compare both formulas, then expand the percentage-load table.
Estimate from a representative set
Repetition-based equations extrapolate from a set performed near the lifter’s repetition limit. A comfortable set stopped early may produce an estimate below actual capacity. Exercise technique, range of motion, fatigue, rest, and equipment affect the relationship between repeated effort and maximal strength. Keep those conditions consistent when comparing results over time.
Why two formulas produce different answers
Epley and Brzycki describe different mathematical relationships between load and repetitions. They can disagree for the same set and agree at ten repetitions in the forms used here. Seeing both numbers helps expose that dependence on the chosen model. Their spread is not a validated confidence interval and does not show which prediction is correct for an individual exercise or lifter.
Round to weights you can actually load
The increment is the change in total load, not the weight of one plate. If adding a 1.25 kg plate to each end increases the bar by 2.5 kg, enter 2.5. The table rounds down rather than adding load above the percentage calculation. A rounded result of zero means the calculated load is below one entered increment. This does not account for a minimum bar weight or every possible equipment combination.
Separate an estimate from a tested maximum
For a single completed repetition, the result is the observed load; there is no need to apply an extrapolation multiplier. For multiple reps, the number remains an estimate. The supported range stops at ten to avoid extending these simple predictions far into high-repetition work, where endurance contributes more to the result.
Percentage rows are calculations for reference, not a prescribed workout or an instruction to attempt the estimated maximum. Use appropriate technique, suitable equipment, and qualified guidance for strength testing. These formulas do not assess injury risk, rehabilitation suitability, readiness on a particular day, or a safe load for a specific person.
Assumptions & limitations
What this calculation assumes
- The entered set represents completed repetitions with comparable technique and load throughout.
- The increment describes a change in the total load in the selected unit.
- Changing the unit reinterprets entered weight and increment values; it does not automatically convert them.
What to keep in mind
- Accepts only 1–10 whole repetitions; model accuracy varies by lift, lifter, and set conditions.
- Neither prediction nor their difference establishes a safe maximum or confidence interval.
- Bodyweight assistance, machine leverage, equipment minimum loads, and rehabilitation needs are not modeled.
Common questions
Can I use this for bench press or squats?
You can enter a completed set for either lift, but the prediction is an estimate specific to that set. Do not assume the same formula has identical accuracy across exercises.
Which formula should I choose?
Both are common prediction methods. Compare them and use a consistent method when tracking comparable sets; the calculator cannot determine which fits your individual lifting performance better.
Why is one rep not multiplied by the Epley factor?
A completed single repetition already demonstrates that load. The tool uses the observed weight for both results instead of increasing it by extrapolation.
Does changing kg to lb convert the inputs?
No. The selected unit applies to the numbers currently entered. Convert your weight and total-load increment before calculating if you switch units.