One Rep Max Calculator (1RM)

Curious what your one-rep max (1RM) might be, but don’t want to gamble on a heavy single? Use this calculator to estimate the maximum weight you can lift for a single clean rep. It works using the weight you already lifted and the number of reps you completed.

Choose kg or lb, enter your set, and you’ll see your estimated 1RM along with training percentages for your next workout. If you also track physique changes alongside strength, the Navy body fat calculator is a simple way to measure progress over time.

For the most dependable estimate, use a weight you can lift with solid form for 1–10 reps. Most lifters get the most consistent results in the 3–10 rep range.

Calculate Your 1RM Instantly (kg or lb)

In one quick calculation, you’ll get:

• Estimated 1RM (yourg key strength number)
• Formula results (several methods, side by side)
• Training percentages (ready-to-use working weights)

Simple, fast, and built for real training sessions—no guessing required. If you want your training numbers to match your fueling, start with the TDEE calculator free and then learn how to calculate macros to set a daily plan that supports recovery.

How to Use the 1RM Calculator

1. Enter the weight you lifted (kg or lb).

2. Enter the reps you completed with good form.

3. Click Calculate (or use auto-calculate).

4. Review:

• Estimated 1RM
• Formula breakdown
• Percentage table for workouts

Best range for accuracy

A challenging set of 3–10 reps is usually the sweet spot. It’s heavy enough to reflect true strength, but not so long that fatigue takes over. Extremely high reps can make the estimate less steady.

What Is a One-Rep Max (1RM)?

Your one-rep max is the heaviest weight you can lift once with proper form. It’s also specific to the exercise. Your squat 1RM can look nothing like your bench press 1RM because each lift uses different muscles, technique, and leverage.

Why Knowing Your 1RM Helps

A reliable 1RM estimate makes training clearer. It helps you:

• Pick a smart working weight (instead of guessing)
• Set intensity using percentages
• Track progress without testing max singles all the time
• Train more safely, with less fatigue and lower risk

And if you like planning heavy days around your routine, a simple period predictor can help you stay consistent with training week to week.

Estimation Methods and Formulas We Use

Why do we show multiple formulas?

Not every lifter responds the same way to reps. Some people shine in low reps, while others do better with slightly higher reps. We show different formulas so you can compare the results and choose the estimate that feels most realistic for your lift and rep range.

Formula breakdown

Let:

• w = weight lifted (kg or lb)
• r = reps completed
• e = Euler’s number (≈ 2.71828)

Brzycki

1RM = w × 36 / (37 − r)

Epley

1RM = w × (1 + r/30)

Lander

1RM = w / (1.013 − 0.0267123 × r)

Lombardi

1RM = w × r^0.10

Mayhew

1RM = w / (0.522 + 0.419 × e^(−0.055 × r))

(Equivalent: 1RM = 100w / (52.2 + 41.9e^(−0.055r)))

How to Read Training Percentages

Quick guide for strength, muscle, and endurance

Use the percentage table to match the load to your goal:

• 60–70%: technique work, lighter training, higher reps
• 70–80%: solid volume for muscle and general strength
• 80–90%: strength-focused work, lower reps
• 90%+: very heavy effort (use sparingly and recover well)

Pick a working weight today

1. Decide on your goal (strength, muscle, or technique).
2. Choose a percentage range from the table.
3. Start on the lower end and adjust based on how your warm-up sets feel.

If warm-ups feel slow or shaky, stay conservative. If everything moves fast and clean, you can push a little higher.

Safety Notes for Heavy Sets

• Warm up properly before hard sets.
• Count only reps with clean form—don’t chase numbers with sloppy technique.
• Use a spotter for bench press or any lift where failing is risky.
• Rest enough between hard sets so fatigue doesn’t break your form.
• If something feels sharp or wrong, stop and lower the load.

Examples

Example 1 (kg):

You lift 100 kg for five reps. Enter 100 and 5 to get your estimated 1RM and working weights for 70%, 80%, and 90%.

Example 2 (lb):

You lift 225 lb for three reps. Enter 225 and 3 to find your estimated one-rep max and training percentages for strength training.

Example 3 (higher reps):

You lift 60 kg for 10 reps. Estimates can change more with higher reps, so the formula breakdown helps you pick a realistic number.