How to Choose the Right Weight in the Gym
Understanding RPE, RIR, and Why “Light” vs “Heavy” Doesn’t Mean Much
One of the biggest mistakes women make in strength training is choosing weights based on arbitrary labels instead of actual effort.
A 15-pound dumbbell might feel heavy for a lateral raise and light for a deadlift. A weight that challenges one person may barely register for another. Your strength changes depending on the movement, your training experience, your recovery, where you are in your menstrual cycle, and even your stress levels that week.
That’s why at Iron and Mettle, we do not coach people using vague categories like “light,” “medium,” or “ heavy.”
Instead, we teach women how to understand effort.
That skill matters far more than memorizing what size dumbbell you “should” be using.
If your goal is to build real strength, muscle, confidence, and long-term progress, learning how to choose the right weight is one of the most important things you can develop in the gym!
What Is RPE?
RPE stands for Rate of Perceived Exertion.
It is a system used in strength training to measure how difficult a set feels. Instead of only focusing on the amount of weight lifted, RPE helps you understand how close you are to your limit while maintaining good form.
A simplified breakdown looks like this:
RPE 5 = Very easy. You could have done many more reps.
RPE 6 = Comfortable effort with plenty left in the tank.
RPE 7 = Challenging, but sustainable.
RPE 8 = Hard work with about 2 reps left.
RPE 9 = Very difficult with maybe 1 rep left.
RPE 10 = Max effort. No reps left. Could not continue for one single extra rep.
The most productive strength training actually happens around RPE 7-9. At Iron and Mettle, we frequently recommend lifting with RPE 8!
That surprises people.
You do not need to destroy yourself every workout to make progress. But you also cannot stay in the “RPE6” zone and expect major changes either.
What Is RIR?
RIR stands for Reps in Reserve.
This is another way to measure effort, and it is closely connected to RPE.
Instead of rating how hard something feels overall, RIR asks:
“How many more reps could I have done before failure?”
For example:
3 RIR = You could have done 3 more reps
2 RIR = You had about 2 reps left
1 RIR = Maybe one more clean rep available
0 RIR = You reached failure
RPE and RIR are essentially opposite sides of the same coin.
Here’s the relationship:
RPE 7 ≈ 3 RIR
RPE 8 ≈ 2 RIR
RPE 9 ≈ 1 RIR
RPE 10 ≈ 0 RIR
These systems help lifters choose weights based on actual training stimulus instead of emotion, ego, or random categories.
Why This Matters for Women’s Strength Training
A lot of people approach weights emotionally instead of objectively.
They choose dumbbells based on:
what looks intimidating
what other people are using
fear of injury
labels like “light” or “heavy”
The problem is that your muscles do not understand labels. They understand tension, effort, and progression.
A 20-pound dumbbell is not inherently “heavy.” Heavy is relative to:
the movement
the rep range
the person lifting it
the amount of fatigue accumulated
For example:
20 pounds may be light for a Romanian deadlift
moderate for a chest press
extremely challenging for a lateral raise
This is why good coaching matters.
At our Noe Valley gym, we teach women to check in with their bodies and select weight based on their own personal RPE and RIR on each movement, each day, at each workout. What is your RPE one day, may feel completely different the following week if for example, you didnt sleep well, you started your period, or you are coming back from extended time away!
What Appropriate Weight Selection Actually Feels Like
One of the hardest things for beginners to learn is that effective strength training should feel challenging, but not impossible.
A properly chosen working weight usually means:
the last few reps slow down slightly
you need focus and control to finish the set
your muscles feel fatigued
your technique still looks solid
For many accessory movements, you will often work around:
RPE 7-8
about 2-3 reps in reserve
For heavier compound lifts, you may occasionally push closer to:
RPE 8-9
about 1-2 reps in reserve
That is where a lot of meaningful strength and muscle adaptation happens.
The Goal Is Not TO ALWAYS GET TO FAILURE
Choosing heavier weights does not mean sacrificing form.
In fact, experienced lifters are usually very good at knowing the difference between:
productive challenge
technical breakdown
unnecessary fatigue
If your posture collapses halfway through a set, the weight may be too heavy.
If the set feels identical from rep 1 to rep 12, it may be too light.
Both extremes limit progress.
Good training usually lives somewhere in the middle:
controlled
challenging
technically sound
progressively harder over time
Why Progressive Overload Requires Honest Effort
One reason many people plateau in the gym is because they stay too comfortable for too long.
Your body only adapts to demand placed upon it.
If the demand never changes:
strength stalls
muscle growth slows
bone density improvements plateau
Progressive overload simply means gradually asking your body to do more over time.
That can mean:
more weight
more reps
improved control
cleaner technique
shorter rest periods
better movement quality
But progressive overload only works if the sets are difficult enough to create adaptation in the first place.
That is where RPE and RIR become incredibly useful. They help you find the sweet spot between undertraining and overdoing it.
“But I Don’t Want to Get Hurt”
This concern is extremely common, especially for people who are newer to lifting.
The reality is that injury risk usually comes from:
poor technique
excessive fatigue
too many reps (junk volume)
inconsistent training
jumping load too aggressively
lack of coaching
Not from appropriately challenging weights.
In fact, resistance training is one of the best tools we have for:
preserving bone density
maintaining muscle mass
improving balance
supporting metabolic health
maintaining independence as we age
preventing injuries and pain
Especially for women over 40.
Research consistently shows that strength training becomes more important as we age.
A Better Question to Ask
Instead of asking:
“Is this weight heavy?”
Ask:
“How many reps do I realistically have left?”
Or:
“How hard did that actually feel?”
That is how we coach our clients each and every day.
Some days a weight moves easily. Some days it does not. Sleep, recovery, stress, nutrition, and hormones all matter.
Good programming accounts for that reality instead of pretending your body performs identically every day.
What We Teach at Iron and Mettle
At Iron and Mettle, we teach women how to:
understand effort
train with enough load to progress
lift with confidence
use barbells and dumbbells safely
build strength progressively over time
Each of these tools help clients understand and learn to listen to thier own bodies and learn how to challenge themselves appropriately - they are no longer left to some arbitrary number of what someone else decided counts as “heavy.”