free calculators

Free fitness calculators from Just GYM

– Train based on figures, not guesswork.
Training without a plan is like training blindly. Our fitness calculators will help you assess where you’re at and plan your next steps – no contracts, no unnecessary red tape, on your own terms, just like the whole Just GYM concept.

Why is it worth using fitness calculators?

Most people at the gym lift weights "by feel" or stick to a weight that hasn’t changed for months. That’s a sure-fire way to hit a plateau. Just GYM’s calculators give you specific figures, which allow you to:

Do you know what weight to choose for strength, hypertrophy or endurance training?

You track your actual progress rather than guessing whether you’re stronger than you were a month ago

You avoid choosing weights at random, which increases the risk of injury

You plan your training cycles (e.g. periodisation) based on your current strength ceiling

Available fitness calculators

1. 1RM Calculator – how much can you actually bench press, deadlift and squat?

1RM (one-rep max) This is the weight you are able to lift once, using the correct technique. It is the basic benchmark in strength training. The calculator will allow you to:

estimate the maximum weight for a given movement without attempting a dangerous maximum lift,
select the training load in % 1RM (e.g. 70% for hypertrophy, 90% for strength),
track progress over time based on successive measurements.

CALCULATE 1RM

BMI calculator – check your body mass index (coming soon)

BMI (Body Mass Index) This is a basic, indicative measure of the relationship between body weight and height, calculated according to the WHO classification. The calculator will allow you to:

quickly check which category (underweight, normal weight, overweight, obese) your result falls into,
treat the result as a starting point for a discussion about your training goal, rather than as a definitive assessment of your physique,
compare it with other metrics (e.g. 1RM), rather than relying solely on a single figure.

How do you use the calculators?

Choose the right calculator for your needs

Choose the tool that best suits what you’re currently working on – strength, mass or fitness.

Treat the result as a starting point

The result from the calculator is an estimate, not a definitive answer. Put it to the test during your next training session.

Update your details regularly

Repeat these calculations every few weeks or whenever you change your training weights, to ensure the figures continue to reflect your fitness level.

Adjust gradually

If the result differs from how you feel during your workout, make a small adjustment (e.g. 2.5–5 kg) rather than changing the whole plan.

What data do the calculators use?

1RM Calculator It uses tried-and-tested, widely used estimation formulas (e.g. Epley, Brzycki), based on the working weight and the number of repetitions performed. The results are indicative and may differ from your actual maximum depending on your technique, training experience and recovery status.

BMI Calculator It is based on the standard WHO formula: body weight (kg) divided by height (m) squared, and compared with the official classification categories (underweight, normal weight, overweight, obese).

Important information for your safety:

Our calculators provide estimates only. The result is a mathematical forecast, not a medical diagnosis. Your body is a complex system influenced by factors such as body composition, hormonal balance and training technique. The content on this website is for information and educational purposes only. Just GYM accepts no liability for training or health decisions made on the basis of the calculator’s estimates. If you are planning radical changes to your training or diet, always consult a trainer, dietitian or doctor.