One Rep Max from 12 Reps

Your heaviest single without actually lifting it

Testing a true one-rep max puts enormous stress on joints, connective tissue and the central nervous system. The smarter approach: lift a submaximal weight for multiple reps and let mathematics extrapolate your ceiling. This calculator runs your numbers through three peer-reviewed formulas - Epley, Brzycki and Lombardi - and averages the results to minimize single-formula bias. It then generates a complete percentage-based training plan from 50% warmup to 95% max attempts.

Quick start

You bench pressed 80 kg for 5 reps.
Epley: 93.3 kg | Brzycki: 90.0 kg | Lombardi: 93.7 kg
Average 1RM: 92.3 kg | Your 80% training load: 73.9 kg

How to use this calculator - step by step

Weight lifted (kg) - enter the weight you successfully completed in your last set. This should be a weight you moved with proper form. Range: 5-500 kg.
Repetitions - the number of clean reps you performed to muscular failure (or near failure). Range: 1-20. Fewer reps produce a more accurate 1RM estimate.
Read your results - three 1RM estimates, their average, a spread indicator showing how much the formulas agree, and a full training plan with weights for every intensity zone from warmup to max attempts.

The three formulas compared

Formula	Equation	Best for	Accuracy
Epley	W x (1 + reps/30)	General use, CrossFit	Best at 3-10 reps
Brzycki	W x 36/(37 - reps)	4-10 rep range	More conservative
Lombardi	W x reps^0.10	Low rep range (1-5)	Best for heavy singles

Training zones by percentage of 1RM

% of 1RM	Training goal	Reps	Rest between sets
50-60%	Warmup, technique	12-15	60-90 seconds
65-75%	Hypertrophy (muscle growth)	8-12	90-120 seconds
80-85%	Strength	3-6	2-4 minutes
90-100%	Power, peaking	1-3	3-5 minutes

Practical examples

Example 1 - bench press
Weight: 80 kg, Reps: 5. Epley: 93.3 kg, Brzycki: 90.0 kg, Lombardi: 93.7 kg. Average: 92.3 kg. Spread: 4.0% - reliable estimate.

Example 2 - squat, low reps
Weight: 120 kg, Reps: 3. Epley: 132.0 kg, Brzycki: 127.1 kg, Lombardi: 134.2 kg. Average: 131.1 kg. Spread: 5.4%. Your 80% training load = 104.9 kg.

Example 3 - deadlift, single rep
Weight: 180 kg, Reps: 1. All three formulas return 180.0 kg. Spread: 0%. With 1 rep, the lifted weight IS your 1RM.

Example 4 - overhead press, high reps
Weight: 40 kg, Reps: 12. Epley: 56.0 kg, Brzycki: 57.6 kg, Lombardi: 50.8 kg. Average: 54.8 kg. Spread: 12.4% - wide divergence. Consider retesting with fewer reps.

Example 5 - training plan
Average 1RM: 100 kg. Warmup: 50 kg (50%). Hypertrophy: 70-75 kg (70-75%). Strength: 80-85 kg (80-85%). Power: 90-95 kg (90-95%).

FAQ

Which formula should I use?

Use the average of all three. Each formula has strengths in different rep ranges: Epley is the most widely used in powerlifting and CrossFit, Brzycki is more conservative and accurate for 4-10 reps, Lombardi works best for 1-5 reps. Averaging smooths out the mathematical differences. If the spread between formulas exceeds 10%, your rep count was likely too high for accurate prediction - retest with 3-5 reps.

How many reps give the most accurate 1RM?

3-5 reps produce the most accurate estimates. At 1-2 reps you are essentially testing your max directly (accurate but risky). At 6-10 reps the formulas still work well but diverge more. Above 10 reps, fatigue factors (cardiovascular endurance, mental toughness, form breakdown) introduce error - the formulas assume pure muscular failure, not cardio limitations.

Should I test 1RM directly or use this calculator?

For most lifters, the calculator is safer and more practical. Direct 1RM testing puts extreme stress on joints and the central nervous system. Competitive powerlifters and Olympic weightlifters need direct testing for competition preparation, but recreational lifters can train effectively using estimated percentages. Test directly only if you have a spotter, proper warmup protocol, and at least 6 months of consistent lifting experience.

How often should I recalculate my 1RM?

Every 4-6 weeks for advanced lifters, every 8-12 weeks for beginners. Beginners progress faster (neural adaptations) so their 1RM changes more frequently, but they also need more recovery time between heavy tests. You do not need to test directly - just input your latest training set data. If you benched 82.5 kg for 5 reps last week (up from 80 kg), recalculate and adjust your training weights accordingly.

What does the "result spread" percentage mean?

It shows how much the three formulas disagree with each other. Below 3% means all three agree closely and your estimate is very reliable. Between 3-5% is normal mathematical variance. Between 5-10% suggests moderate disagreement, often from mid-range reps. Above 10% indicates significant divergence, usually from testing with too many reps (above 10). A lower spread means a more trustworthy 1RM estimate.

Does 1RM differ between exercises?

Yes, significantly. A typical intermediate male lifter might have: squat 1RM = 140 kg, deadlift 1RM = 160 kg, bench press 1RM = 100 kg, overhead press 1RM = 65 kg. Each exercise involves different muscle groups, leverage and range of motion. You need to calculate and track 1RM separately for every lift. The percentage-based training plan applies to each lift individually.

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