What Does 3-5 Ft Surf Mean? How Waves Are Measured
Surf forecast height is significant wave height (Hs) — the average of the tallest third of waves measured by NDBC buoys. Face height (what you see) runs 1.5-2x the forecast number. So a '3-5 ft' forecast means 4.5-10 ft wave faces. Hawaiian scale uses roughly half of face height, adding further confusion.
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Key Takeaways
- Forecast height (Hs) is 60-70% of face height. Multiply the forecast by 1.5-2x to estimate what you'll actually see.
- Three scales exist: significant height (buoy/forecast), face height (what you see, 1.5-2x Hs), and Hawaiian scale (~0.5x face height).
- Calibrate forecast numbers to your local break by comparing predictions to what you actually see over several sessions.
The Short Answer
Surf forecast height is significant wave height (Hs) — the average of the tallest third of waves measured by NDBC and CDIP buoys. Face height (what you actually see at the beach) runs 1.5-2x the forecast number. So a "3-5 ft" forecast means roughly 4.5-10 ft wave faces. Hawaiian scale uses roughly half of face height, adding further confusion. Always ask: which scale is being used?
The Three Wave Measurement Scales
Significant wave height (Hs): Used by NOAA, WaveWatch III, and most forecast models. It's a statistical measure from buoys — the mean of the highest third of waves over a 20-minute sampling window. This is what you see on Quiver and most forecasting apps.
Face height: What surfers actually see standing on the beach. A 3-foot Hs reading from a CDIP buoy translates to roughly 4.5-6 foot faces, depending on the break's bathymetry. Sandy beach breaks tend toward the higher multiplier; deep-water reefs toward the lower.
Hawaiian scale: Used in Hawaii and by some old-school surfers. Roughly half of face height (or close to Hs). A "6-foot Hawaiian" wave has a 10-12 foot face. If someone in Hawaii says "it's 4 feet," prepare for 8-foot faces.
“Three scales exist: significant height (buoy/forecast), face height (what you see, 1.5-2x Hs), and Hawaiian scale (~0.5x face height).”
What This Means for Your Session
When Quiver shows "4 ft at 14 sec," expect 6-8 foot faces at most beach breaks. Beginners comfortable in 3-foot faces should look for forecasts of 1.5-2 ft Hs. Don't compare numbers across apps without checking their measurement convention — Surfline, Quiver, and Windguru may use different scales or conversions. The best calibration: surf your local break at a known forecast, compare what you see, and build your personal conversion factor. After 10 sessions, you'll know that "3 feet on Quiver" means exactly what at your spot.
Frequently Asked Questions
Why don't forecasts just use face height?+
Significant wave height (Hs) is a standardized measurement from buoys. Face height varies by beach — the same swell produces different face heights at different breaks due to bottom contour, refraction, and focusing effects. Hs is the objective, comparable number.
Is a 6-foot wave dangerous for beginners?+
If that's 6-foot face height, yes — that's overhead and can hold you under. If it's 6-foot Hs, it means 9-12 foot faces, which is very large surf. Beginners should stay in 1-3 foot face height (roughly 0.5-2 ft Hs).
Why do Hawaiians measure waves differently?+
Historical tradition from the 1960s-70s surf culture. Hawaiian surfers measured from the back of the wave, not the face. The convention stuck. When a Hawaiian says '10 foot,' they mean a 15-20 foot face — it's not modesty, it's a different ruler.
What's the biggest wave ever measured by a buoy?+
NDBC buoy 46005 recorded significant wave heights over 50 feet during North Pacific storms. The largest individual waves in those events likely exceeded 90-100 feet face height. These are open-ocean measurements, not surfable coastline waves.
