The Real Foundation of a Sleep Guide: Your Baby's Individual 24-Hour Sleep Need

If there's one concept I come back to with every single family I work with, it's this: every baby has their own personal 24-hour sleep need, and it's different to every other baby's. Once you understand this, it becomes obvious why so many wake-window charts and sample routines you'll find online simply don't work, no matter how consistently you follow them.

What Do I Mean by "24-Hour Sleep Need"?

Your baby's 24-hour sleep need is the total amount of sleep their body actually requires across a full day and night. Not the amount they "should" be having according to a chart. Not the amount their cousin or best friend's baby gets. The amount that their body, with their own biology, genuinely needs.

This total is then split between night sleep and daytime naps. The majority of that sleep will always be concentrated overnight, with naps making up the smaller remaining portion, though exactly how that balance looks shifts as your baby gets older. But the starting point is always the same: a single 24-hour number that belongs uniquely to your baby.

Why Sleep Need Varies So Much Between Babies

Just as adults vary in how much sleep they need to feel rested, babies vary too, and the differences can be significant. I generally talk about this in terms of high sleep need and low sleep need babies.

High sleep need babies can comfortably sleep for long stretches at night and take substantial naps during the day. They tend to do well on the longer end of any age-based "average" you'll find online.

Low sleep need babies simply don't require, or can't physically sustain, anywhere near as much sleep. They might wake earlier, nap for shorter periods, or need less daytime sleep overall, not because anything is wrong, but because that's what their body is built for.

Neither is better or worse. They're just different, and the strategy that works for one will often fail for the other.

Why Generic Routines Can't Account for This

Most of the wake windows and sample routines circulating online are built around averages. They take a baby's age and assign a "typical" amount of awake time and sleep, based on what tends to work for most babies at that stage. As a rough starting point, that's not a bad thing. The problem is when it's treated as the answer, rather than a guide.

A generic routine has no way of knowing whether your baby is high or low sleep need. It just assumes "average," and average doesn't actually describe most individual babies particularly well.

When you try to apply a routine built for a high sleep need baby to a low sleep need baby, you're effectively asking their body to sleep more than it's able to.

When this happens, the same kinds of issues tend to show up: short naps, split nights, and real difficulty settling at bedtime or naptime with false starts. These aren't usually a sign that something has gone wrong with your approach. More often, they're a sign that the schedule and the baby's actual sleep need are out of step with each other.

This is also why "it worked for my friend's baby" doesn't tell you much. Their baby's sleep need and yours could sit at completely different points on the spectrum, so comparing routines without accounting for that rarely gets you anywhere useful.

So What's the Right Number for My Baby?

There isn't a number I can hand you that applies to every baby of a given age, because that's exactly the trap generic routines fall into. The only way to know your baby's true 24-hour sleep need is to track it directly, by logging their actual sleep over several days and averaging the total.

I've written a full step-by-step guide to that process, including how to use the number to build a routine, here: How to Calculate Your Baby's Sleep Need and Build a Routine Around It.

And if you're approaching sleep training, this number isn't just helpful background information, it's essential groundwork. I explain why in Why You Must Calculate Sleep Need Before Sleep Training.

The Takeaway

Your baby's sleep need is personal to them. Understanding it, rather than borrowing a number from a chart or another family's experience, is the foundation that everything else in their sleep routine should be built on.