How Big Are 18 Inch Arms?

18 Inch Arms

Big arms are a hallmark of physical fitness and strength. And everyone loves an action hero with big guns.

That’s why arm curls are one of the most popular exercises at the gym. So how do you know if your arms are average or exceptional?

Well, upper arm circumference is a yardstick by which many measure their progress. And 18 inch arms are a common benchmark among bodybuilders and fitness athletes.

But how big are 18 inch arms? Read on to find out!

What Are 18 Inch Arms?

Arm size is a circumference measurement of the mid-upper arm. So “18 inch arms” are 18 inches (45.7 cm) around the widest part of the bicep and tricep.

How to Measure Your Arms

Before getting into arm sizes, make sure you’ve measured your arm accurately. Arm size is measured using a flexible tape such as a tailor’s tape.

First, raise one arm parallel to the floor and drape the end with the number “1” over the front of your bicep. Then wrap the other end of the tape around the widest part of your arm until the numbers overlap the end.

How To Measure Arms

The number that intersects the end of the tape is your arm size. As you can see in the image above, bodybuilders measure their arms flexed.

Tips: Do not pull the tape too tight or your arm will appear smaller. Also do not wrap the tape at an angle or your arm will appear bigger.

Are 18 Inch Arms Big?

Generally speaking, 18 inch armsAnythingy larger than average size. Anything over 14.6 inches is above average for men. And over 13.4 inches is above average for women.

However, you might want to be more than “above average.” And 18 inch arms could be on the small side if you’re a competitive bodybuilder or have a massive frame.

Whether your arms look big on your body depends on your age, height, weight, and body composition.

18 Inch Arms by Age

Age is one of the most apparent factors influencing your arm size because we all start with skinny arms as children and grow through our teenage years.

Once you reach adulthood, your arm growth slows down. However, most people’s arms get a little bigger through their 20s and 30s.

At some point in your 40s, however, your arms might gradually get smaller. This decline is due to the drop in hormones and decreased physical activity.

Table 1. Average Arm Size By Age For Men & Women (Unflexed)

Age Men Women
20-29 13.4 inches (34.1 cm) 12.4 inches (31.5 cm)
30-39 14.1 inches (35.9 cm) 12.9 inches (32.8 cm)
40-49 14.0 inches (35.6 cm) 13.1 inches (33.3 cm)
50-59 13.7 inches (34.8 cm) 12.9 inches (32.8 cm)
60-69 13.5 inches (34.4 cm) 12.8 inches (32.4 cm)
70-79 13.1 inches (33.2 cm) 12.6 inches (32 cm)
80+ 12.1 inches (30.8 cm) 11.7 inches (29.6 cm)

The data in the chart above comes from the National Center for Health Statistics in the US. But it’s important to realize that these measurements are taken with the arm relaxed or unflexed.

Arm Size Flexed vs Unflexed

When you flex your bicep, your arm increases in size roughly 5-10%. So a 13.5” unflexed arm is generally about 14.5” flexed.

And, since you probably measured your arm flexed, it’s vital to adjust the data from the previous table to compare apples to apples. Below is the revised arm size data based on the estimated size increase with a flexed bicep.

Table 2. Average Arm Size By Age For Men & Women (Flexed)

Age Men Women
20-29 14.4 inches (36.6 cm) 13.3 inches (33.7 cm)
30-39 15.2 inches (38.6 cm) 13.9 inches (35.3 cm)
40-49 15.1 inches (38.4 cm) 14.1 inches (35.8 cm)
50-59 14.7 inches (37.3 cm) 13.9 inches (35.3 cm)
60-69 14.6 inches (37.1 cm) 13.7 inches (34.8 cm)
70-79 14.1 inches (35.8 cm) 13.5 inches (34.3 cm)
80+ 13 inches (33 cm) 12.5 inches (31.8 cm)

In Table 2, you can see that the average man’s arms typically don’t get much over 15 inches. Therefore, 18 inch arms are about 20% bigger than average for men.

For women, the average arm size is a little smaller at 13½ inches. And 18 inch arms would be equally exceptional for a woman.

To put this arm size data in perspective, it helps to look at it in terms of percentiles. These charts show how likely you are to have arms of a specific size.

Table 3. Arm Size Percentiles For Men & Women (Flexed)

Percentile Men Women
5th 11.9 inches (30.3 cm) 10.5 inches (26.8 cm)
10th 12.6 inches (31.9 cm) 11.1 inches (28.1 cm)
15th 12.9 inches (32.8 cm) 11.4 inches (28.9 cm)
25th 13.4 inches (34.1 cm) 12 inches (30.6 cm)
50th 14.6 inches (37.1cm) 13.4 inches (34.1 cm)
75th 16 inches (40.7cm) 15.2 inches (38.5 cm)
85th 16.9 inches (42.9 cm) 16.2 inches (41.2 cm)
90th 17.4 inches (44.2 cm) 17.2 inches (43.7 cm)
95th 18.4 inches (46.7 cm) 18.2 inches (46.1 cm)

Now you can see that a man or woman with 18 inch arms is in the 95th percentile. In other words, your biceps are bigger than at least 19 out of 20 people.

But you probably aren’t having a flex off with an 80-year-old. So here are some charts to help you visualize how big 18 inch arms are based on a normal distribution of arm sizes for people ages 20-59.

18 Inch Arms Percentiles Men
18 Inch Arms Percentiles Women

18 Inch Arms by Weight

Also, how much you weigh determines how big your arms look on your body. For example, 18 inch arms look much bigger on a 180-lb guy than a 250-lb guy.

In other words, the heavier you are, the bigger your arms must be to look impressive. Obviously, you want that weight to be muscle, not fat. I’ll get into that in a minute.

18 Inch Arms by Height

Finally, your height also affects how big your arms look.

To illustrate, picture a 5’6” person standing next to a 6’6” person. If they both have 18 inch arms, the short guy’s arms will look much larger.

So the taller you are, the bigger your arms must be to look impressive.

Arm Size Calculator

Height, weight, and age make it difficult to know if your arms are considered big. Fortunately, there are equations to predict average arm size based on these variables.

I created a simple calculator that shows you if your arms are big or small for your demographic.  

arm size calculator

Enter the information below to see if your arms are bigger than other people your age and size.

18 Inch Arms by Body Fat Percentage

There are a couple of other factors to consider that are not included in the arms size equation. One of them is your body fat percentage.

Having more muscle and less fat makes your arms appear more prominent. The reason is that you can see the separations between your arm and shoulder. And sometimes even the muscle striations and veins.

In addition, being leaner makes your arms look bigger compared to your arm joints (wrist, elbow) and your waist.

For example, below is what I look like when bulking vs cutting. My arms are about 16 inches in both pictures, but they look way better when I’m lean!

18 Inch Arms Bulk vs Cut

I weighed 198lbs on the left and 171lbs on the right and I’m 5’9″ tall. It goes to show that 16″ arms look bigger when you’re lean. I should also note that I had an arm pump in both pictures.

Arm Size Pump vs No Pump

It’s also important to realize that increased blood flow to your arms while working out makes them swell up in size – aka the pump. So measuring your arms right after arm exercises can add 0.5-1″.

For accuracy, it’s best to measure your arms without a pump. That way, you see your true arm size and not just how much volume you did on bicep curls.

Of course, it is fun to occasionally measure your arms with a massive pump to see how big you can get them! But, just take the inflated measurement with a grain of salt and know that’s not how big your arms typically are.

How To Grow Your Arms

Building a big set of arms takes more than just repping out sets of bicep curls. Instead, you need a well-rounded plan, including nutrition, workouts, and a few proven supplements.


Believe it or not, how you eat is more important than how you lift when building muscle. You won’t progress very far in the gym if you don’t give your body what it needs to grow.

First, you need to create a calorie surplus to gain muscle consistently. That means you eat more calories than you burn each day.

Calorie Surplus For Bulking II

Next, you must eat enough protein to give your arms the building blocks to grow new muscle tissue. And don’t listen to that 1 gram of protein per pound of bodyweight bro science!

Your lean mass, activity level, and fitness goal dictate how much protein you need.

Calculate Your Grams of Protein Per Day

Some other nutrition advice I have is to eat mostly clean foods. Skip the junk and steer towards whole, natural foods for the most quality gains.

Also, tap into nutrient timing to unlock the last 10% of potential arm gains. That means getting most of your carbs and calories around your workout.

bodybuilding meal plan

Custom Meal Plan

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To build big arms, you need to train your whole body. That may sound counterintuitive, but compound exercises like squats and deadlifts boost muscle-building hormones that help you build big arms.

As for your biceps, they are made up of an inner and outer head. The inner head creates size and thickness, while the outer head adds to the peak. So include a variety of exercises to hit both bicep heads.

Hammer Curls vs Bicep Curls For Peak & Width

18 Inch Arms Outer Bicep Workout

Also, don’t forget to train your triceps because they make up approximately 2/3 of the area of your arm! Therefore, big triceps make it easier to build 18 inch arms.


As a word of caution, do not expect supplements to grow your arms in days or weeks miraculously. Instead, supplements are only an add-on to proper diet and exercise that may give you a slight boost.

In addition, there are a lot of snake oil supplements that cost a lot of money and don’t deliver results. Here are some proven muscle-building supplements that can help you build bigger arms.

How Long Does It Take to Get 18 Inch Arms?

The time it takes to get 18 inch arms depends on your starting point. For example, if you’re relatively new to training and already have 17 inch arms, you could reach 18 inches in a matter of months.

On the other hand, it could take you a year or more if you’ve been lifting for a while and need to gain more than an inch of arm size. Also, keep in mind that not everyone can attain 18 inch arms. It requires good genetics and years of hard work.

How To Build Your Arms Faster

Now you know how 18 inch arms measure up. But if you want to grow your arms in weeks instead of months, you must start with a dialed-in muscle gain meal plan.

And you can get a personalized, easy-to-follow nutrition plan right here. Click the image or button below to learn more about Custom Meal Plans for Muscle Growth.

bodybuilding meal plan nutrition
Big Arms Diet

With this information, you’re well on your way to building an impressive pair of arms. However, here is some additional reading that I think is most relevant to you.

Average Wrist Size Male & Female

Long Head Tricep Exercises

Lateral Head Tricep Exercises

Medial Head Tricep Exercises

Short Head Bicep Exercises

Long Head Bicep Exercises

And if you liked this article, check out some of my other helpful content below!

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