When you check a surf forecast, one number often stands out: the wave period. Sometimes called the swell period or interval, this little number (usually in seconds) can tell you a lot about how your next surf session might go.
But what exactly is wave period—and why does it matter?
A Simple Breakdown
At its core, the wave period is the time it takes for one wave crest to pass and the next one to arrive at a fixed point. You’ll see it expressed in seconds—like 7 seconds, 10 seconds, or even 16 seconds.
Imagine standing on a pier or looking out at a buoy. Count the seconds between two wave peaks passing the same spot—that’s your wave period. It’s not just a number; it’s a snapshot of the ocean's rhythm.
Why Should Surfers Care?
Because the wave period tells you about a swell’s strength, speed, and even how far it traveled to get to your local break.
Generally, longer wave periods mean more powerful, better-formed waves. These swells—known as groundswells—come from distant storms and build energy as they travel across the open ocean. When they hit your beach, they often result in clean, lined-up sets with more size and consistency.
Shorter periods, on the other hand, usually mean the swell was created by local winds. These windswells tend to be messier, weaker, and more unpredictable—though sometimes still surfable, especially for beginners or those just looking to get wet.
What Do Different Wave Periods Tell You?
While every surf spot reacts differently to swell, here’s a general guide to help you interpret what you see in a forecast:
Wave Period
What to Expect
1–4 seconds
Too weak to surf—choppy and wind-driven with little to no form.
5–6 seconds
Still disorganized and usually not worth the paddle unless you’re really eager.
7–9 seconds
Short-period windswells that can bring okay conditions, especially with the right wind direction.
10–12 seconds
Solid mid-range swells—good energy, better shape, often fun and manageable for most surfers.
13–15 seconds
The sweet spot for many breaks. These are clean groundswells with power and well-defined sets. A great time to paddle out!
16+ seconds
Big, long-traveling swells generated far from shore. These carry serious energy and are perfect for points and reefs that can handle the punch. Not ideal for every break—or every surfer.
