One Rep Max Calculator UK, 1RM & Training Percentages

One Rep Max Calculator

Calculate 1RM from any weight & rep count

Weight Lifted

Your Bodyweight (for standards)

Reps Performed

reps

1 rep5101520 reps

Squat 1RM

- Bodyweight

Est. 5RM

Est. 3RM

Est. 10RM

Formula Comparison

Weight

Zone

Reps

Purpose

Next Milestone

3-Month Target

6-Month Target

1RM estimates are most accurate when calculated from 1-5 rep sets performed close to failure. Estimates from higher rep sets (10+) become progressively less accurate as fatigue affects the relationship between reps and percentage of 1RM.

The Guide

How To Calculate Your One Rep Max

Your one rep max (1RM) is the maximum weight you can lift for a single repetition with good form. It's the foundation of strength programming, knowing your 1RM lets you calculate precise training weights for every rep range and intensity zone.

Directly testing your 1RM carries injury risk and requires significant recovery time. Estimating it from a sub-maximal set (a weight you can lift for 2-10 reps) is safer and accurate enough for programming purposes, especially when averaged across multiple formulas.

The 7 Formulas Used

Formula	Equation	Best For
Epley	w - (1 + r/30)	Most widely used, good all-rounder
Brzycki	w - 36 / (37 - r)	Most accurate for low reps (1-10)
Lander	w - 100 / (101.3 - 2.67 - r)	Good mid-range accuracy
Lombardi	w - r^0.10	Tends to produce higher estimates
Mayhew	w - 100 / (52.2 + 41.9 - e^(-0.055 - r))	Accurate for higher rep ranges
O'Conner	w - (1 + 0.025 - r)	Simple, slightly conservative
Wathan	w - 100 / (48.8 + 53.8 - e^(-0.075 - r))	High-rep accuracy

Training Percentage Zones

Once you know your 1RM, you can prescribe exact training weights for different goals. Each percentage zone produces different physiological adaptations, using the right zone for your goal is how you train smarter rather than just harder.

Zone	% of 1RM	Rep Range	Primary Adaptation
Absolute Strength	90-100%	1-3	Neural efficiency, max strength
Strength	80-90%	3-5	Strength + muscle
Strength-Hypertrophy	70-80%	6-8	Balanced strength and size
Hypertrophy	60-70%	8-12	Muscle size, optimal range
Muscular Endurance	50-60%	12-20	Endurance, rehab, warm-up

How Often Should You Test Your 1RM?

For most lifters, recalculating your 1RM estimate every 4-8 weeks is sufficient. After a training block of 8-12 weeks with progressive overload, your actual 1RM will have increased and your training percentages need updating. Rather than maxing out directly, take a rep PR (a new best with any weight for any reps) and plug it in here to get an updated estimate.

Frequently Asked Questions

Testing your true 1RM carries a higher injury risk than sub-maximal training, especially for beginners. For most people, estimating from a 3-5 rep set is accurate enough and far safer. If you do test directly, always use a spotter on pressing movements, use a squat rack with safeties, and ensure your technique is solid before attempting maximal loads.

Accuracy decreases as rep count increases. Sets of 1-5 reps produce the most reliable estimates, within 2-5% of actual 1RM for most people. Sets of 6-10 reps introduce more variability due to individual differences in muscular endurance. Sets above 10 reps should be treated as rough estimates only, as fatigue and endurance factors dominate over pure strength.

No, training too close to your 1RM every session leads to accumulated fatigue, injury risk, and stalled progress. Most effective programming uses a variety of intensities across the week. A common approach: one heavy day (80-90%), one moderate day (70-80%), and one lighter day (60-70%) per movement pattern per week.

As a general benchmark for men: Squat 1.5- BW (intermediate), 2- BW (advanced). Bench 1- BW (intermediate), 1.5- BW (advanced). Deadlift 2- BW (intermediate), 2.5- BW (advanced). OHP 0.75- BW (intermediate), 1- BW (advanced). Women's standards are roughly 65-70% of these. These are rough benchmarks, everyone's build affects leverage and therefore what's achievable.

One Rep Max