Free One Rep Max Calculator

What is a One Rep Max (1RM)?

A one rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's considered the gold standard for measuring maximal strength and is widely used by coaches, athletes, and fitness enthusiasts to design training programs and track progress.

Knowing your 1RM allows you to calculate the appropriate weight for different training goals—whether you're training for strength, hypertrophy (muscle growth), or muscular endurance.

Why Estimate Instead of Test?

While directly testing your 1RM is the most accurate method, it comes with several drawbacks:

• Injury risk — Maximal lifts put extreme stress on muscles, joints, and connective tissue
• Requires experience — Proper form under maximal load takes years to develop
• Needs a spotter — Safety requires qualified assistance
• CNS fatigue — True maximal efforts tax your nervous system for days
• Not practical for all exercises — Some movements are dangerous at true max

Estimation formulas allow you to get a reliable approximation using submaximal weights, which is safer and more practical for most people.

1RM Estimation Formulas

Several formulas have been developed to estimate 1RM. Each has slightly different assumptions and may be more accurate for certain individuals or rep ranges.

Rep Percentage Chart

Once you know your 1RM, you can use these percentages to determine training weights for different rep ranges:

Reps	% of 1RM	Training Focus
1	100%	Max Strength Testing
2	97%	Strength/Power
3	94%	Strength
4	92%	Strength
5	89%	Strength
6	86%	Strength/Hypertrophy
7	83%	Hypertrophy
8	81%	Hypertrophy
9	78%	Hypertrophy
10	75%	Hypertrophy
11	73%	Hypertrophy/Endurance
12	71%	Muscular Endurance

Training Applications

Strength Training (1-5 reps)

Training at 85-100% of your 1RM with low reps develops maximal strength by recruiting fast-twitch muscle fibers and improving neural efficiency. This is the rep range used by powerlifters and strength athletes.

Hypertrophy Training (6-12 reps)

Training at 65-85% of your 1RM with moderate reps maximizes muscle growth by creating metabolic stress and mechanical tension. This is the classic bodybuilding rep range.

Endurance Training (12+ reps)

Training below 65% of your 1RM with higher reps improves muscular endurance and work capacity. This is useful for athletes needing sustained performance.

Tips for Accurate Estimation

• Use 3-6 reps — Formulas are most accurate in this range. Higher reps introduce more variables.
• Be fresh — Test when not fatigued from previous sets or workouts.
• Use strict form — Cheating reps will inflate your estimated 1RM.
• Use compound lifts — Formulas work best for squat, bench, deadlift, and overhead press.
• Average multiple formulas — Using "Average All" can smooth out individual formula biases.
• Retest regularly — Your 1RM changes as you get stronger. Retest every 4-8 weeks.

Limitations

Sample Training Program Using 1RM

Here's an example of how to use your 1RM to structure a 4-week strength block:

Week	Sets × Reps	% of 1RM
Week 1	4 × 6	75-80%
Week 2	4 × 5	80-85%
Week 3	5 × 3	85-90%
Week 4 (Deload)	3 × 5	70%

After the deload week, you can retest your estimated 1RM and begin a new training block with updated weights.

Safety Considerations

• Always warm up thoroughly before heavy lifting
• Use a spotter for bench press, squats, and overhead movements
• Learn proper form before increasing weight
• Don't test actual 1RM if you're new to lifting (use estimation instead)
• Listen to your body—sharp pain means stop immediately
• Progress gradually; jumping weights too fast causes injuries