One Rep Max Calculator – Introduction
Your one-rep max is the foundation of many strength training programs because they involve lifting a prescribed percentage of your one-repetition maximum, or 1RM for short.
However, if you are a newer lifter, you may not know what your 1RM is or how to discover it.
Also, you might want to know how to manipulate your one-rep max to elicit various changes to your body.
This article lifts the lid on this interesting topic, provides you with several ways to determine your one-rep max, and discusses why you may want to use alternative weight prescription methods in your workouts.
One Rep Max Definition
What does one repetition maximum (aka one rep max or 1RM) mean, and why does it matter?
Your 1RM is the maximum amount of weight you can lift in a given exercise.
It’s the heaviest weight you can lift once, but not twice.
Think of your one-rep max as your current personal record.
You can find your one-repetition maximum for almost any exercise, but it’s rarely necessary to know your 1RM for exercises such as calf raises, tricep dips, or bent-over rows.
Instead, for most exercisers, 1RM is best reserved for those big, important compound exercises, such as the squat, bench press, and deadlift.
If you are an Olympic lifter, you may add front squats, clean and presses, and snatches to the list.
A lot of workouts specify how much weight you should lift in terms of your one-rep max.
For example, you might have to do five sets of five reps with 85% of your one-rep max.
Those same workouts may also be progressive, using a different set and rep scheme and 1RM percentage from one week to the next, for example:
1. Week 1 – 5 sets of 5 reps @ 85% 1RM
2. Week 2 – 4 sets of 4 reps @ 90% 1RM
3. Week 3 – 3 sets of 3 reps @ 95% 1RM
4. Week 4 – 2 sets of 2 reps @ 100% 1RM
5. Week 5 – 1 set of 1 rep @ 105% 1RM
This is called a peaking program and is designed to increase and then test strength.
You could also use it in your preparation to compete in a Powerlifting competition.
Of course, to do any of these programs, you first need to know your one-rep max!
How to calculate 1RM
There are several ways you can estimate your one rep max.
The most obvious way is to go into the gym and see how much you can lift, but that approach can be more than problematic for beginners.
It can pose a serious risk of injury.
Instead, learn how to do a “real” 1RM test as suggested at the end of this section.
But, in the meantime, some alternative methods may be better for beginners.
#1. Hashi Mashi’s One Rep Max Calculator
Based on your input, Hashi Mashi’s one rep max calculator will expand to show you the estimated weights and reps you can lift.
The method for calculating your 1 rep max is based on Epley’s equation.
Step 1: Select your units, pounds, or kilograms.
Step 2: Adjust the amount of weight and reps you tested with.
Warning: Do NOT attempt to lift the absolute max you think you can.
That’s the purpose of a one rep max calculator, so you can estimate your one-rep max, not actually lift it!
Some of the strongest men who ever walked the earth like Hermann Goerner, never even attempted their 1 rep max!
Additional apps and websites
There are several apps and websites you can use to work out your 1RM.
They use one of several calculations to estimate your one-rep max based on the number of repetitions you can do with a given weight.
All you need to do is warm up, load up your bar, and rep out to failure.
Enter the weight and the number of reps performed into the app/website, and you’ll get your estimated 1RM instantly.
In addition, most apps and websites will also give you a list of 1RM percentages, usually from 50 to 100%, that you can then use for programming purposes.
Other good apps and websites for estimating your 1RM include:
#2. Use a calculation
You can also work out your one-rep max yourself with a simple calculation.
You’ll still need to rep out to failure and make a note of the weight you lifted, and the number of reps performed.
There are several methodologies to choose from, but this one is one of the best.
Weight x reps x 0.0333 + weight = e1RM (estimated one repetition maximum)
For example, if you performed six reps with 100 pounds and were unable to complete a seventh:
100 x 6 x 0.0333 + weight = 119.98 pounds or 120 lbs rounded up.
You can use the same 1-rep max formula for kilograms as well.
So, if you’re a more advanced lifter using heavier weights:
100 x 6 x 0.0333 = 19.98 + 100 = 119.98 which we’ll round up to 120 kg – the nearest workable weight plate denomination.
But Hashi Mashi’s Weight Lifting Calculator is much simpler to use:
#3. 1RM coefficient
Another way to estimate your one-rep max is to use a coefficient.
Using this method, you simply do a maximum effort set between two and ten reps, note how many reps are performed, and then multiply the weight by the appropriate coefficient.
For example, if you perform six reps with 100 kilos
100 x 1.18 = 118 kg
As you can see, this comes out very close to the predicted one rep max in the previous example.
You can use several coefficient tables, but this one from the American College of Sports Medicine is as good as any.
In the ACSM coefficient chart, the upper body and lower body estimated 1RMs are predicted differently.
This reflects the average muscle fiber variation between the upper body and the lower body.
#4. Ramping up to your one-rep max
If you want to discover your true 1RM, ramping up is arguably the best way.
It is, however, not without risks.
You will be lifting heavy weights, for starters, and the heavier the weight, the greater your risk of injury.
Plus, if you are a beginner, your body (muscles, joints, tendons, and ligaments) may not be ready for the demands of lifting your maximum weight.
Also, as a beginner, you may not be physiologically skilled enough to do a good 1RM test.
Therefore, ramping up is a good technique for more experienced lifters.
It takes time to learn how to generate maximal force.
If you’re used to doing sets of six, eight, or ten reps, you may struggle to fire off all your muscle fibers at the same time, as you need to do for a 1RM attempt.
Because of this, it’s worth spending a few weeks working up to your IRM test, doing workouts of progressively fewer sets, and heavier reps.
To ramp up to your 1RM, after your warm-up, do a single repetition with a relatively lighter weight – around 50% of your anticipated 1RM.
Rest a moment, add around 5 – 10% to the bar, and lift again.
Keep adding weight rep by rep until you max out.
Try to hit your 1RM in 5-8 attempts.
Rest 2-3 minutes between early attempts and 3-5 minutes as you get closer to your maximum.
Remember, you MUST try one more weight, even if you think you’ve reached your limit.
That’s how you prove you’ve actually hit your 1RM.
Otherwise, you may end up leaving your actual 1RM in the tank because you stopped your test too early.
However, ramping up is not for everyone.
As mentioned before, even Hermann Goerner, whose feats of deadlift strength over a hundred years ago will leave you speechless, never lifted his one-rep max!
Instead, use the following strength assessments:
#5. Upper and lower body strength assessments
The National Academy of Sports Medicine (NASM) recommends the following method to estimate your one-rep max:
- Warm-up with a light weight for 8 to 10 reps
- Rest for 1 minute
- Add 5 – 10 percent of the initial load and do 3 to 5 repetitions
- Take a 2-minute rest
- Repeat steps 3. and 4. until you hit failure between 3 and 5 reps
Use Hashi Mashi’s one rep max calculator to show you the estimated weights and reps you can lift based on your input.
Step 1: Select your units, pounds, or kilograms.
Step 2: Adjust the amount of weight and reps you tested with.
Follow the same steps for a lower-body strength assessment, such as squats and deadlifts, except you can increase your initial load in step 3 by 10 – 20 percent.
But, do you REALLY need to know your 1RM?
There is a problem with the reliability of the 1rm test results – they can vary from one day to the next.
You could be firing on all cylinders one day and crank out a new 1RM, and then, because maybe you’re tired, feeling overtrained, or just aren’t very psyched up for your workout, show up at the gym weaker than the day you achieved your best.
Or, if you tested your 1RM on a “bad day,” you could have underestimated your 1RM, and you’re actually stronger than it suggests.
If your workout uses percentages of your one-rep max, you could find yourself blasting through some workouts too easily and unable to complete others, all because your 1RM wasn’t 100% accurate.
Also, workouts that prescribe things like four sets of six with 70% of your 1RM ignore the fact that your first set will feel easy because you are well-rested, but your last set could be a real grinder because you’re tired.
The reality is that only the middle two sets will be in the sweet spot of ultimate productivity.
Because of this, some lifters use other methods alongside or even instead of 1RM to ensure they train hard enough to progress, but not so hard they cannot recover between workouts.
Rating of perceived exertion
Known as RPE, this method originated in the world of endurance sports but has since become popular in strength training too.
When using RPE for strength training, instead of performing a set number of reps with a given weight, the number of reps is determined by how you feel and the level of intensity you want to reach.
Because RPE is relatively new to strength training, there is no standardized RPE scale.
However, the one below provides a good idea of how you should feel at any given level of intensity.
An RPE of 1 – 3 isn’t relevant – the weight is too light to produce meaningful results.
4: Recovery; usually 20 plus rep sets; not hard but intended to flush the muscle
5: Most warm-up weights
6: Light speed work; weight moves quickly with moderate force
7: Weight moves quickly when maximal force is applied
8: Weight is too heavy to maintain fast bar speed but isn’t a struggle; 2–4 reps left
9: Last rep is challenging, but there is still one rep left in the tank
10: Max effort, no reps left in the tank
How to use the RPE scale
Using this information, you can regulate your training effectively and in a way that takes into account how you feel from one workout to the next, and even one set to the next.
For example, in the past, your workout might have called for five sets of five reps with 85% of your one-rep maximum.
However, instead, you choose to do five sets with 85% of your 1RM to RPE 9.
Your workout could end up looking like this:
1. Set #1 – 6 reps (feeling fresh so did an extra rep)
2. Set #2 – 5 reps
3. Set #3 – 5 reps
4. Set #4 – 4 reps (starting to tire – form would have been bad if you did another rep)
5. Set #5 – 3 reps (Really feeling tired now – two more reps with good form out of the question)
Five really high-quality sets, all taken to the same level of exertion, but auto-regulated based on how you felt.
No form breakdown, no risk of injury grinding out the last few reps, and no unnecessary reps that would simply delay recovery.
Just a very productive workout.
Another useful way to monitor the intensity of your workout is bar speed.
As before, if your workout calls for five sets of five with 85% of your 1RM, you may find that your physical condition on the day means you can do more or less than what is prescribed.
Bar speed will tell you how well your set is going.
If you notice bar speed decreasing, and you have to grind out your reps, you’re probably too tired and should stop your set.
But, if the bar is moving at the same speed as it did at the beginning of your set, stopping could rob you of another couple of productive reps, so you should keep going a little longer.
You can also use your form to determine when you should bring your set to an end.
Simply stop each set as you notice your technique starting to deteriorate.
If your form is solid, keep going for another 1-2 reps, even if it’s more than the prescribed rep volume.
But, if you start to falter sooner than expected, stop your set.
The bottom line is that if you don’t vary your performance from workout to workout, and even one set to the next, to reflect your energy levels at that exact time, you may find yourself training too hard or not hard enough to get the results you want.
That’s the main drawback of getting too obsessed with your one-rep max and “locked-in” to a percentage-based program.
Make your workouts more productive with the following items of gear:
A good 1RM requires focus and aggression. A sniff of smelling salts hits you like a slap in the face to fire you up and clear your mind.
They smell HORRIBLE, but some lifters find them very stimulating.
These Ward Bottled Insanity Smelling Salts are insanely powerful, so, use them with caution!
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Based on percentage training but with some nice twists, this is a workout for beginner, intermediate, and advanced exercisers.
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One Rep Max Calculator – Wrapping Up
While it’s nice to know your 1RM, especially for measuring progress, it’s not essential.
So long as you add weight to the bar week by week, you will get stronger, even if you don’t know what your ultimate single-rep performance is.
If you are a beginner and want to know your 1RM, estimate it using a strength assessment with Hashi Mashi’s One Rep Max Calculator, a coefficient table, calculation, website, or app.
Then use RPE or one of the other methods to adjust your workout intensity from one week to the next, to avoid under or over-exertion.
If you are more experienced, the ramping and strength assessment methods work well.
However, don’t test your one-rep max too often – it’s not only exhausting, but doing so increases your risk of injury!
By all means, try a percentage-based program; they can work for some lifters.
But, if you find some workouts too easy and others too hard, you won’t be alone.
That’s why RPE is gaining popularity in strength training – it allows for those natural energy peaks and valleys that straight-line percentage-based programs cannot accommodate.
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