What’s the Best Age to Start Potty Training?

A simple breakdown of when most toddlers can handle daytime vs. nighttime potty training.

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The way potty training stories float around a playground or parents' group, you’d think there must be some magic timing to it.

We waited until she was this age and it only took a weekend!

No pull-ups at night? That won't work until your child is older. They grow into holding it.

Turning a year older — two, three, four — does bring new skills and big changes. So it makes sense that parents wonder:

Is there a certain age when potty training just… clicks?

And the real question underneath is:

How old should you start potty training in the day (and at night)?

Below is a simplified breakdown of what we actually see with age and potty training — based on development, pattern, and what most toddlers can realistically handle.

(And while we’re on the topic of birthdays and milestones, scroll to the end for the sweetest birthday tradition we started in toddlerhood — my favorite find for kid birthdays.)

Is there a magical age when potty training (in the day or night) is easier?

1. The 20 - 30 month window

In Oh Crap Potty Training, we talk about the ideal time to start potty training as the window between 20 months and 30 months.

Why this age range?

There’s a natural lull after kids have mastered all the big gross-motor stuff: walking, running, climbing, and generally being tiny toddlers on the move. Things are a little quieter before they approach age three.

Once kids move closer to three, they hit the individuation phase (aka the age of “I do it myself!” and “No, actually, YOU do it.”). That independence streak is amazing for growth, but can add an extra layer of challenge to potty training.

And to be clear:

This doesn’t mean you’re doomed if you start earlier or later.

It’s just the sweet spot we see most often for how children can handle the process.

Jamie talks a lot about the Oh Crap Signs of Readiness, and how the whole “wait until they’re ready” mindset ties into age and timing. This is where parents get tripped up, so the age window helps demystify things.

You can also time everything just right, and some kids will start withholding pee. 👉 Here's how to help your child release pee.

2. What’s the Best Age to Start Nighttime Potty Training? (It Depends!)

For nighttime potty training, age matters far less than patterns. If your child has a stretch of five to seven dry nap diapers or nighttime diapers, that’s your golden window to drop the sleep diapers — no matter how old they are.

There’s one big exception:

If your child is three years old, you want to lean in and address night training. The bladder is forming by around age four, and you don’t want it to form without nighttime holding or consolidation. Otherwise, the chance of long-term bedwetting goes up.

🌝 If you want to read up on how to drop the night diapers, my post on timing night training shares tips on how to drop the night diapers.

3. But My Toddler Sleeps in a Crib. Should We Still Start Nighttime Potty Training?

In Oh Crap Potty Training, we recommend starting night training either before you begin daytime training or at the same time you drop night diapers. The key is simple: your toddler needs to be able to get to the potty when they feel the pee. That means having a small potty near the bed and a clear path for them to use it.

In a crib, that just isn't possible.

Historically, most kids transitioned out of a crib around age two. But in the past few years, I’m hearing more and more from families whose preschoolers — even three- and almost four-year-olds — are still in a crib. And that later transition can affect potty training in a couple of ways:

• It limits self-initiation. A child can’t act on the urge to pee if they’re physically trapped.

• It makes night training tougher. You end up lifting a heavy toddler out of a low crib multiple times a night, which is rough on your body and adds extra steps to the process.

From an autonomy standpoint, the crib-to-bed transition is important. Jamie talks about this a lot: helping toddlers build independence without tipping into tiny dictator territory. When a child sleeps in a crib, they literally start their day needing an adult to pick them up.

And there are a few reasons why we see that transition lagging later can affect potty training — both with self-initiation to go pee in the potty as well as making the potty training night training process more difficult.

When a child is in a crib, they literally start their day needing you to pick them up.

For a toddler at the potty training age, you want them practicing independence instead:

Climb out of bed (which is another good pelvic floor movement for their body).

Pee in the potty.

Poop in the potty.

I can do it myself.

The sweet spot is timing these milestones close together so the confidence and momentum build on each other.

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And Now for the Fun Part I Wanted to Share With You…

You're doing all the big, important work now — helping your toddler build independence, pee and poop in the potty, even holding pee overnight. These are important milestones.

But there's also something so tender about this age. And sometimes it helps to balance the skill-building with a moment of magic.

Here's one tiny ritual that we've absolutely loved in our house, and it's become a treasured part of every birthday. If you look closely at the cover, you'll see the book is well-worn from years of flipping through it for birthday ideas.

This is our Birthday Book.

our special birthday book

At bedtime on the eve of a birthday, I pull out this book and read a few tales from the Stories section — changing the main character’s name to match my child’s. Kids get a huge kick out of hearing themselves in the story.

Then I give them the same number of goodnight kisses as the age they’re turning and read the sweet little verse titled Two Verses to Be Said the Night Before the Birthday.

And in the morning, the magic continues. We start birthdays with a walk downstairs to the dining table where presents wait, and little paper hearts mark the birthday trail. It’s simple, but it feels special.

All of these simple, sweet ideas come from this book.

Now that my kids are older (and still insist on doing all the same rituals), it’s clear which parts became core memories.

It’s not the toy they got when they turned three.

It’s not the cake icing I stayed up late perfecting when they were six.

It’s these tiny details, repeated year after year.

It’s knowing they’ll hear the birthday poem.

It’s knowing we’ll read the birthday stories.

It’s knowing they’ll do their birthday walk and then — poof — their day officially begins.

And honestly, I love the old-school charm of the Birthday Book. It's full of the kind of simple childhood magic that's easy to forget in a Pinterest world, including:

Including...

• age-appropriate birthday party games (even ones I played as a kid)

• simple recipes

• birthday traditions from around the world

• homemade decoration and gift-wrap ideas

We've used this birthday book to mark each year— each trip around the sun — with a simple, sweet sense of celebration. It's honestly one of my favorite parenting finds.

With this little ritual, it always feels like we're ushering in a new age together. And as Jamie so often speaks about the importance of connection with your child at every age, this birthday book has become one of those tools that brings a deeper connection and a steady, comforting rhythm to our birthdays.

That, to me, feels like a bit of parenting magic!

FAQ: When to Start Potty Training (Day and Night)

Q: What’s the best age to start daytime potty training?

The sweet spot is usually between 20 and 30 months. This window tends to fall after the big physical-skill stage (walking, climbing, running) and before the strong independence streak around age 3, which can make potty training more challenging.

Q: How do I know when to stop using night diapers?

If your child has 5–7 dry nights or dry nap diapers in a row, that’s your signal to drop night diapers. And if your child is over age 3, you’ll want to start supporting night training even if those dry nights haven’t appeared yet.

Q: Is it okay to keep my toddler in a crib while night training?

Not really. Night training works best when toddlers can get to the potty on their own, and that’s not possible in a crib. A toddler bed or floor bed gives them access and makes the process much smoother.

Q: What if my child is over 3 and still in diapers at night?

By 3 to 3.5 years old, it’s time to start helping with night training. By around age 4, the bladder finishes forming, so supporting overnight holding and consolidation now helps prevent long-term bedwetting.

Q: Do milestones like moving from a crib to a bed affect potty training?

Yes — these milestones often work hand in hand. Shifting from crib to bed and practicing small independence routines (like getting up and going to the potty on their own) can strengthen overall potty training progress and confidence.