From Crib to Big Kid Bed: The Complete Toddler Mattress Size & Transition Guide

Your baby’s world changes fast. One day, they’re tiny in their crib, the next they’re climbing over the rails and declaring their independence. If you’re wondering when to move from a crib to a toddler bed and what mattress size you actually need, you’re in the right place.

This guide will help you understand standard toddler mattress sizes, when to make the switch, and how to make it easy, safe, and stress-free for everyone.

What Size Is a Toddler Mattress

Most parents are surprised to learn that a toddler mattress is the same size as a standard crib mattress. In the United States, that’s typically 27¼ inches wide and 51⅝ inches long (about 69 x 131 cm).

So if your crib converts to a toddler bed, you don’t need to buy a new mattress. You can reuse the one your baby has been sleeping on, as long as it’s still firm, clean, and in good condition.

Here’s a simple breakdown of common mattress sizes:

If you’re still setting up your nursery, explore our baby cribs. Many styles, like the Soho 3-in-1 Convertible Crib, transition beautifully from crib to toddler bed to daybed. Crafted in Italy from renewable beechwood, it’s non toxic, GREENGUARD Gold Certified, and built to last through every stage of childhood.

When To Make The Switch

Every child is different, but most toddlers transition to a bed between 18 months and 3 years old. The key is to watch for readiness rather than focusing on an exact age.

Here are some signs your little one might be ready:

1. They’re climbing out of the crib

Once your toddler starts trying to scale the rails, it’s a safety concern. Pediatric experts recommend switching once your child reaches around 35 inches tall or consistently climbs out.

2. They’re feeling cramped

If your toddler looks uncomfortable or frustrated in their crib, it may be time for more space to stretch and move.

3. They’re potty training

Having the freedom to get out of bed helps with nighttime bathroom trips and independence.

4. You’re expecting another baby

If a new sibling is on the way, transitioning early can help your older child adjust to their “big kid” role while giving you time to reuse the crib.

How To Make The Transition Easier

This stage can be emotional for parents and exciting for toddlers. A few thoughtful steps make it much smoother.

Keep the same mattress and bedding. Familiar textures help your child feel secure.

Add safety rails. Guardrails prevent accidental falls during the early weeks.

Choose a low bed frame. A floor bed or low toddler bed makes it easier for your child to get in and out safely.

Stick to your bedtime routine. The same songs, stories, and snuggles create comfort and predictability.

Make it special. Let your toddler help pick new sheets or a favorite bedtime toy to celebrate the milestone.

Safety and Comfort Tips

• The mattress should fit snugly in the frame with no gaps around the edges.

• Keep it firm and supportive to protect your toddler’s growing spine.

• Skip pillow top or overly soft styles until they’re older.

• Use breathable, lightweight bedding only.

• Always check that your bed meets ASTM and JPMA safety standards.

At dadada, every crib and toddler bed is built with these same standards in mind. Our finishes are VOC free, PFAS free, and GREENGUARD Gold Certified for cleaner air and a healthier sleep space. Because a good night’s sleep starts with safe materials and pure air.

When To Move Up To A Twin Bed

Most toddlers are ready for a twin bed around age four, or when they begin to outgrow their toddler frame. Moving too early isn’t necessary. If your toddler sleeps well and has room to move, staying in their 3-in-1 convertible setup can be more comforting and practical.

The goal is to grow with your child, not rush through the stages.

The Takeaway

A toddler mattress usually matches your crib mattress, making this milestone simple and stress free. Focus on your child’s cues, safety, and comfort, and choose furniture designed to grow with them.

With dadada’s 3-in-1 convertible cribs, you get a timeless piece that adapts from baby to big kid, crafted from solid beechwood with non toxic finishes. It’s more than furniture. It’s peace of mind, sustainability, and safe sleep built to last for generations.

Healthier Sleep. Happier Baby.