Terminal Hair Length: Is it Determined by Genetics?

“Oh, it’s because they have long hair in their family.”

“We’re not hairy in my family, that’s why.”

How often have you heard these?

More importantly, how true are they?

Is terminal hair length determined by genetics?

Find out below!

Oh wait, you may want to check this Summary of Genetics and Terminal Hair Length first; I made it for you!

What is Terminal Hair Length (THL)?

Terminal hair length, or THL, is the highest length your hair can successfully attain.

Yes, it’s a thing.

There’s a specific maximum length your hair can grow to. That does not mean it stops growing when it reaches that length; hair never stops growing.

Instead, it means any growth after that length gets naturally nullified by shedding off or breakage.

Now, do genetics determine your terminal hair length?

My Research: Do Genetics Determine Terminal Hair Length (THL)?

The question has always puzzled me, too, so I decided to find out firsthand.

I conducted a brief survey to find out how much genetics generally affect hair length.

A total of 32 individuals responded to these questions:

Do females in your immediate family (mum, sister) have about the same hair length?
If yes, do you all have the same level of interest and practice in hair care?
If not, do you all have the same level of interest and practice in hair care?

The result?

56% of females confirmed having about the same hair length as others in their family. Of these 56%, 22% have the same interest and practice in hair care, while 34% have different interest levels.

This shows that a larger percentage of females have the same hair length as others in their family, even when they have different levels of interest in hair care.

Apparently, genetics have a solid role to play in determining hair length.

Out of the 44% with varying hair length in their family, only 6% have the same level of hair care interest.

The remaining 38% have varying hair care interests (some more, some less).

That shows that it’s also very possible for people within the same family to have different hair lengths, and in most cases, it’s because they have different levels of hair care practices.

What’s the point?

Genetics do play a major role in determining terminal hair length.

In simpler terms; your parents, where you’re from, can determine how long your hair can grow.

Many studies have confirmed this, mentioning genetics as a key factor affecting hair loss and growth.

For example, genetics determine how long your hair lasts in the first stage of hair growth — the anagen phase.

The anagen stage is where your hair grows.

It can last between two to six years, depending on your genetics.

Studies have mentioned that hair grows at a rate of 0.5 inches per month.

So, if your anagen phase lasts two years, for example, you should naturally achieve 12 inches.

If your genetics allow your anagen phase to last up to five years, you’ll naturally have 30 inches.

Genetics can also cause medical conditions that affect hair growth, like androgenetic alopecia, which affects up to 50% of males and females.

However, genetics is not the only factor determining hair length (more on this in a bit).

Your hair care practice also has a role to play, as seen by the varying hair length in many families with varying interests in hair care.

Your hair care practice determines whether you reach your THL successfully.

So, the fact that your hair has stayed at a particular length for years does not mean that length is the THL dictated by your genetics.

In fact, there’s a really high chance you’ve not reached your terminal hair length when you think you have.

Take me as an example…

My Experience: Terminal Hair Length and Hair Care

I learned the ~~hard~~ long way that hair care practices affect hair length almost as much as genetics.

This was my hair in 2021, 5 years after growing it with very little knowledge about hair care.

In January 2022, I did the big chop and started regrowing my hair. This time, I had the needed knowledge about hair care and followed the dos and don’ts.

Here’s my hair two years later (January 2024), and as you can see, it’s longer than it was at five years old.

I’m still the same person with the same genetics, so what changed?

I got serious with my hair and cared for it like I should.

It would have been easy for me to conclude in 2021 that that was my terminal hair length.

I mean, it didn’t grow longer than that for a long time.

But in just two years, I achieved a length longer than I had for five years.

That means that my 2021 length was not my terminal hair length.

I just wasn’t harnessing my hair length well enough.

It could be the same for you.

What you think is your terminal hair length (simply because your hair has not grown past it for many years) could actually be just half of your hair length potential.

Logically, the shortest possible terminal hair length is about 12 inches.

Why?

Remember how long the anagen phase can last?

Two to six years.

So if your genetics are “unlucky,” then you’ll have the shortest possible anagen phase — two years.

Hair grows 0.5 inches per month, so do the math — 12 inches.

All the hair on your head cannot be in the anagen phase at the same time, so no one is saying you should definitely have 12 inches after two years.

But realistically, if you’ve grown your hair for about three to five years, 12 inches should be the very least.

So, instead of sitting back and erroneously concluding that your hair is not growing past a certain length because of your genetics, get serious with hair care, choose the right products for your hair, and see what happens.

You just might be surprised at how much your hair can still grow!

Now, what does “get serious with hair care” really mean?

How to Increase Your Hair Length No Matter Your Genetics

I’ll be sharing tips that helped me grow my hair longer in a shorter period.

These tips can help anyone (no matter their genetics) to boost their hair length.

It takes time and commitment, but they work effectively.

1. Hydrate and Moisturize

I’ve said this in many posts: moisture and hydration are very important in growing hair.

Think of how many things can’t survive with water: plants, animals, even humans.

Our hair is no exception.

If you want to grow your hair, start with hydration and moisturizing.

Hydration means you drink enough water daily and spritz your hair with water regularly.

Moisturizing involves using leave-in conditioners and moisturizing shampoos.

2. Use Hair Oils

Whenever you hydrate/moisturize, you should seal in that moisture with hair oil.

Applying moisture to your hair without sealing it in is like filling a gas cylinder and leaving the valve open — it becomes pointless.

There are different types of hair oils that work well, like coconut oil, jojoba oil, argan oil, lavender oil, and olive oil.

Choose one that suits your hair (that doesn’t itch or leave it too oily or dry) and apply it consistently after moisturizing it.

3. Make Protective Hairstyles

Protective hairstyles include braids, twists, and cornrows. They are called “protective” because they tuck in your hair ends and prevent everyday combing and detangling.

You should make these styles if you want to increase your hair length.

But when you do, avoid making them too tight because then they become less protective.

Also, keep moisturizing and oiling your hair even when wearing protective hairstyles.

That’s something that has become part of me: applying a reasonable amount of leave-in conditioner (I use the mega growth daily leave-in strengthener) and hair oil (coconut oil) to my scalp/hair while on braids or other styles.

Aside from nourishing your hair for growth, it also helps your style last longer.

4. Cover Your Hair to Bed

Are you fond of sleeping without a satin/silk bonnet?

Well, that’s a wrong move if you want your hair to grow fully to its terminal length.

Rubbing your hair against pillows and bedsheets increases breakage, which we don’t want.

So get a satin/silk bonnet and wear it to bed. Alternatively, use a satin/silk pillowcase.

5. Trim Split Ends

There’s been controversy recently about whether trimming really helps hair growth.

In my opinion, it does.

Here’s the logic: when you don’t trim split ends, they split further and eventually fall off.

That means you’ll be having more inches falling off.

But when you trim them off as soon as they appear, you lose tiny inches and save more hair.

The only valid reason to ignore trimming is if you never have split ends.

And honestly, that’s almost impossible.

To be safe, trim your hair every two to three months.

And in case you’re wondering, yes, I do that too.

6. Explore Natural Hair Ingredients

We’ve had different hair ingredients come and go: rice water, onion water, and, more recently, rosemary and cloves.

I’m not saying you should jump on every hair trend that pops up on TikTok or YouTube, but these natural hair ingredients do work, too.

Be realistic, and don’t expect some magical overnight hair growth.

At the very least, these ingredients will nourish your hair and encourage hair growth.

But if you succeed at being consistent with them, yes, they’ll grow your hair faster.

I’m currently exploring rosemary and cloves, and I’ll share my results soon in a blog post!

7. Cultivate Good Hair Habits

To help your hair grow to its terminal length, some things must become a part of you. Little things like how you comb, loosen, and detangle your hair goes a long way. Here are a few tips:

Always finger-detangle your hair first. Don’t just dip a comb in it immediately.
Moisturize your hair before combing; don’t comb it dry.
Whenever you shampoo your hair, follow it with a conditioner.
Use heat styling tools (dryers, straighteners, or curling irons) sparingly. Don’t make them too often.

Other Factors Affecting Hair Length

Have you ever met someone with really long hair, and when you ask them, they say, “I don’t do anything to it.”

No special care or hair products.

That’s genetics at play.

But you know what’s the truth in such cases? Their hair would grow longer than that if they did pay attention to hair care.

So, apart from genetics, other factors affect hair length like:

1. Diet

How and what you eat affect your hair growth.

When you’re well-nourished with the proper nutrients like biotin, iron, and vitamin D, your hair will grow as it should.

A person who’s malnourished might as well never reach their terminal hair length.

Research confirms that nutrition plays a crucial role in hair loss and growth.

Health

Your general health and well-being also play a role. Stress can hinder hair growth, while a healthy lifestyle encourages hair to grow as it should.

Also, there are hormones (like androgens) that control hair growth, so hormonal changes can also affect hair.

For example, some women have reported rapid hair growth during pregnancy.

Also, underlying medical conditions can prevent hair from growing as it should.

Hair Care

As mentioned, hair care goes a long way when it comes to hair length.

Moisture, protein, and protective styling are all important factors in helping your hair reach its terminal length.

If you do not pay attention to all these areas, you cannot say you’ve reached your terminal hair length.

There’s a high chance your hair can still grow longer.

Key Takeaway

Is terminal hair length determined by genetics?

Yes, your genetics determine the highest length your hair can attain.

Does that mean that since your hair has not grown past a certain length for years, that length is your terminal length?

NO, other factors are involved, too.