Sometime between 14-18 months your little dreamer will drop down to one nap. Your little dreamer will also tell you when he/she is ready by skipping one of their naps for two weeks straight. Yes, I really do mean two weeks. The problem with making the transition before you see a solid two weeks of only one nap is your child may just be experiencing a sleep regression. One of the most common results of transitioning too early is a chronic earlier riser (4-5am). And it is dreadful. However, if two naps are a struggle you might consider capping each nap to one hour and lengthening wake times before making the switch to one nap. It doesn't matter which nap your child skips or if they alternate between skipping the morning one and the afternoon one. As long as one nap is skipped for 14 days your kiddo is ready. When your little one skips their morning nap you will opt for an earlier (11:30am) nap and then early bedtime. If the afternoon nap is skipped consider moving bedtime up by the normal length of their second nap. For example, if the second nap is usually one hour and bedtime is usually at 7pm, you would move bedtime up to 6pm when the second nap is skipped.
When you begin the transition to one nap you will push the first nap back to at least 11:30am. Ideally your child would take a three hour nap here, but you are more likely to get 1-2 hours. Remember that delaying getting your child up after a nap will help lengthen the nap. It can take up to 30 days to lengthen this nap. You will want to time bedtime to be 4 hours after your child wakes from their nap, with 5:30pm being the earliest you would do bedtime. Remember that each day or few days you will continue to push the nap later and later until it is happening at 12:45pm. I say 12:45pm even though the nap is actually starting at 1pm. Getting your toddler to bed for this nap on time is so important. A late nap will make your toddler resist sleep and take a shorter nap. Aim to get your child in bed at 12:45pm and if you are just a couple minutes late you should be okay. Some younger toddlers may keep the nap between 12-12:30pm for a little bit. Remember the most important part of your one nap schedule will now be timing bedtime 4 hours after your child wakes from their nap.
Here is a generic example of what your schedule might look like before and after the transition:
7am wake up
10-11am first nap
3:00-4:00pm second nap
7am wake up
Eventually, around two or two and half years, your child will be ready for a little bit more awake time after their nap and you can move bedtime to 4.5 hours after waking from the nap. This nap will stick around till at least 3 years and up to 4 years, but the 4.5 hours stays pretty consistent until the nap is dropped. And rest assured you will have plenty of nap strikes thrown in there. ; )