Are 13-Inch Biceps Big? (Here’s How to Make Them Grow)

To put it bluntly … no.

But while your 13-inch flexed biceps are definitely below average for men 20-and-up, there’s still hope that you can turn them into 15, 16, or 17-inch beasts.

Here’s how to make those pain-in-the-ass, why-does-my-DNA-hate-me 13-inches grow.

More About 13-Inch Biceps

Now, we said that 13-inch biceps are kind of twiggy, which they are. We know that because the CDC collected anthropometric data — a fancy way to say “body measurements” — in 2015–18.

Of the 4,617 men aged 20–80 studied, the average biceps sizes were:

Age Group	Average Biceps Size (Likely Unflexed)
20–29	13.41 inches
30–39	14.13 inches
40–49	14.02 inches
50–59	13.70 inches
60–69	13.54 inches
70–79	13.07 inches

The CDC doesn’t specify whether these are flexed, relaxed, or ‘pumped” measurements. But if we had to guess, we’d say measurements were taken with the arms hanging at the sides.

This means that your 13-inch biceps are actually punier than you thought. Flexed, the average upper-arm measurement for 20–29-year-old guys is likely closer to 14–15 inches.

But we also can’t ignore the fact that “biceps measurements” aren’t just the biceps brachii. It also includes the brachialis — the muscle lodged beneath the biceps brachii — and the triceps — the three-headed muscle at the back of the arm accounting for 60–70% of upper arm mass.

Keep these facts in mind as we walk you through this five-step strategy!

Step 1 – Stock Up On the Right Supplements & Equipment

Arnold Schwarzenegger didn’t earn the name “Austrian Oak” and wind up with 22 ¾-inch biceps with 15-pound curls and diamond push-ups. (Granted, he did have a little “extra” help.)

To move onto 14-inch upper-arms and beyond, you need the right combination of:

Supplements

No powder or pill will ever replace a balanced diet and a hypertrophy-based training program. But if unfortunate genetics of stubborn biceps are to blame, these three supps can help:

Creatine

Creatine is one of the most well-studied sports supplements on the planet, and for good reason. This non-essential amino acid — AKA: your body can make its own — is one of the primary fuel sources in skeletal muscles that your body taps into during resistance training workouts.

It also increases the release of a growth hormone called IGF-1 and pulls water into the muscle cells, creating the illusion of even thicker muscles.

An 8-week 2017 study compared the benefits of creatine vs. placebo during a four-day split program. After a week-long loading dose and a 7-week maintenance dose (0.03 g/kg per day), the creatine group increased tissue mass in the upper body significantly — +7.1% vs. +1.6%.

Whey Protein

Whey protein is what we call a “complete protein” — a blend of the nine essential amino acids that support muscle repair and recovery post-workout.

The ACSM recommends 0.5–0.8 grams of protein per pound of body weight to increase muscle size. However, if you’re a hard-gainer with a low appetite, a scoop of whey protein can provide an instant 20–40g dose of protein after a tough arms workout.

Pre-Workout

Pre-workout is one of the more polarizing supplements on the market.

While many argue that these supplements are nothing more than placebo power-ups, the 100mg (or more) of caffeine in each dose suggests otherwise. Caffeine can deliver a jolt of energy, focus, and stamina when taken an hour before training.

Research from 2020 also revealed that athletes who ingested caffeine before a 4×8 bench trial (at 70% of their 1RM) performed more mechanical work and recorded a higher power output boost than the placebo group. Of course, higher volume training is the key to muscle growth.

Fitness Equipment

The other half of the journey toward the Goblet of Gains (that was too clever not to borrow from the Buff Dudes) is either joining a gym or building out your own makeshift home gym with:

Adjustable Dumbbells

We have nothing against old-school dumbbells. But at $1.50/pound and clunky as all get-out, they’re not exactly practical for a small home gym or tight budgets. Adjustable dumbbells allow you to easily add and remove weight for exercises like hammer curls and kickbacks.

A Barbell & Weight Plates

Barbells and weight plates are the foundation of any decent home gym setup. But aside from the Big Five lifts, they’re also compatible with popular biceps and triceps exercises like close-grip bench presses and barbell curls.

An Adjustable Bench

Whether you’re using it as a makeshift preacher curl bench or cranking out incline curls and skull crushers, an adjustable bench is another must-have for beefier bis and tris.

A Pull-Up Bar

The final piece of equipment to make your upper arms explode is a pull-up bar. A straight bar is fine, though if you want to eventually develop your V-taper with more pull-up and chin-up variations, consider one that includes wide, narrow, and neutral grips.

Step 2 – Master Those Upper Arm Exercises

Those 13-inch rattlesnakes (let’s be honest — you’re about nine inches shy of Hulk Hogan’s “pythons”) won’t grow without the perfect combination of biceps and triceps exercises.

To add height and width to your future cannonballs and horseshoes, consider these moves for your training routine:

Biceps Exercises

• Barbell curls or EZ bar curls, which activate the full biceps brachii and brachioradialis more effectively than dumbbell curls
• Incline biceps curls to target the long head of the biceps and build a steeper peak
• Hammer curls to inflate the brachialis muscle beneath the biceps brachii
• Preacher curls, which better target the biceps’ short head and add width

Triceps Exercises

• Single-arm overhead dumbbell extensions to activate the largest part of your triceps — the long head
• Cable rope pushdowns, which target the medial head closest to the elbow
• Barbell skull crushers to bulk up to the outer side of your triceps muscle

Train Compound Lifts, Too

The biceps and triceps also act as synergists — or assist muscles — during many upper-body compound lifts targeting the back and chest. We call the primary muscle contracting during an exercise the “agonist,” which would be either the pecs or a back muscle in this case.

The back and biceps work together during exercises like:

• Lat pulldown
• Medium-grip pull-up (which research shows are better than narrow-grip)
• One-arm dumbbell row

The “push” muscles like the chest and triceps team up during:

• Bench press (especially variations with narrower grips)
• Push-up
• Chest dip

These multi-joint exercises are no replacement for isolation exercises if your goal is 14+-inch arms. But adding them to your routine can increase your training volume, and research shows exercises like lat pulldowns may be equally effective for biceps growth as curls in newbies.

Step 3 – Follow the Science & Hypertrophy Training Principles

What works for you won’t always work for your gym buddies — and vice versa. But even though we all have a different genetic make-up and a unique split of type 1 (endurance) and type 2 (power) muscles, there’s plenty of research into how to best increase hypertrophy.

One 2019 review concluded that the best way to maximize growth were:

Of course, deviating from these goals won’t leave you a 13-inch shrimp forever. In fact, that same study recommends drop sets, pyramid sets, supersets, and various training loads to bust through ego-destroying plateaus (which could explain why you’re stuck at a flat-13).

A 2019 trial also supports partial reps for some triceps exercises. The eight-week, 3-day-a-week study found a significant increase in triceps cross-sectional area with partial reps compared to standard reps (+48.7% vs. +28.2%).

Stick to those guidelines when you can, but don’t be afraid to add some variety if growth stalls or you’re becoming bored.

Step 4 – Allow Your Muscles Proper Rest

More is better when we’re talking about the principle of progressive overload — or increasing your training volume as your muscles become stronger. However, each high-load rep will cause microscopic tearing in your muscle fibers and weakness, both requiring time for full recovery.

By “recovery” and “rest,” we mean two things:

During Workouts

Training to muscle failure sparingly won’t necessarily undo your gains. But in 2016, researchers discovered that failure training isn’t any more effective for building strength or hypertrophy than leaving 2–3 reps in the tank.

The best piece of advice we can give you about weight selection is: Choose a weight that allows you to reach the upper-end of your rep goal while stopping just short of failure. Once you can meet the rep goal for all sets without cheat reps, increase the weight by 2.5 or 5 pounds.

Another common question is how long to rest between sets.

According to one 2009 review, 30–60 seconds is the gold standard for increasing growth hormone release and building mass.

Additional research from 2010 suggests something similar. In this study, those resting for 60 seconds between sets saw increased growth hormone concentrations in the blood compared to those resting for 90 or 120 seconds.

Between Training Sessions

Training bis and tris every day — or even every other day — isn’t just a recipe for disaster. It also increases your odds of overtraining, bulging tendons (tendonitis), and muscle tears.

But just how many days of rest should you leave between arm workouts? If we listen to the research, schedule 48–72 hours between workouts is your best bet.

One particular study from 2019 led participants through 10RM testing for three exercises to compare recovery rates at 24, 48, 72, and 96 hours. While performance declined 24–36 hours post-exercise, the muscles returned to full strength by the 48 and 72-hour marks.

A push-pull-legs (PPL) or classic four-day split will nurture growth in your biceps and triceps without overtraining!

Step 5 – Eat for Growth

You can kiss your dreams of 15, 16, or 17-inch biceps “goodbye” if you’re fueling your body like a ‘98 Honda Civic hand-me-down instead of a straight-off-the-lot Bugatti La Voiture Noire.

To add inches to your upper arms through diet:

Create a Caloric Surplus

It’s entirely possible to build muscle without being in a caloric surplus — or taking in more calories than you burn. Hell, you can even pack on muscle mass while in a caloric deficit, though the rate of growth depends on how much protein you eat.

But, generally, adding 10–20% to your maintenance calories is the most efficient way to ensure hypertrophy and add 0.25–0.50% to your bodyweight weekly. At least that’s how bodybuilders bulk up in the off-season, according to 2019 research.

Perfect Your Macro Split for Mass

Unfortunately, the strategy of the IIFYM — of “If It Fits Your Macros” — won’t work here. So to force your biceps and triceps to grow into the above-average territory, you’ll need to eat a specific split of proteins, carbohydrates, and fats.

Now, we know you’re not an elite bodybuilder or anything. (No offense to you and your 13-inch biceps.) But bodybuilders are some of the best examples of pushing the human physique to its limits and maximizing muscle potential.

Before contests and during the off-season, bodybuilders leave 55–60% of their daily calories to carbohydrates, 25–30% to protein, and the final 15–20% to fats.

So if you have a 2,500-calorie goal, that’d equate to 1,375–1,500 calories from carbs, 625–750 from protein, and 375–500 from fats.

It’s not an exact science, though!

How to Help Your 13-Inch Biceps Grow …

Increasing the size of your 13-inch biceps isn’t as simple as just supplements, or just training, or just changing your diet. It’s actually a combination of all three with a five-step approach:

1. Stock up on the right supplements & equipment.
2. Master those upper arm exercises.
3. Follow the science & hypertrophy training principles.
4. Allow your muscles proper rest.
5. Eat for growth.

Most importantly, allow your body and muscle time to grow. The proud owners of the biggest biceps in bodybuilding history didn’t cut corners or expect inches of growth in months.