How to read a tide chart
A tide chart looks like a wave because it is one — it shows how the water height at a location rises and falls through the day. Here’s how to read one quickly and use it to plan your time on the water.
The curve is water height over time
The horizontal axis is time (left to right across the day) and the vertical axis is the predicted water level. As the curve climbs, the tide is rising (flooding); as it falls, the tide is falling (ebbing). The smooth shape comes from the steady pull of the moon and sun, which is why tides are so predictable.
Highs and lows
The peaks are high tides and the valleys are low tides. Most U.S. coasts see one or two highs and lows per day, depending on the location. On Tide Compass each peak and valley is labeled with its height and time (for example, H 2.5 ft or L 0.3 ft), so you can see at a glance when the water will be highest and lowest.
What the heights mean (the datum)
Heights are given in feet relative to MLLW — Mean Lower Low Water, the average of the lower low tides. Think of it as the “zero line.” A reading of 2.0 ft means the water is two feet above that average low mark; a negative tide means the water is predicted to drop below it, exposing flats and sandbars that are usually covered.
The “NOW” line
The vertical marker labeled NOW shows the current time, and the readout tells you the present height and whether the tide is rising or falling. Hover or drag across the chart to read the predicted height at any time — handy for picking a launch or return window.
“6-min” vs “interpolated”
NOAA publishes two kinds of data. Primary stations have full 6-minute predictions, giving a precise curve. Many smaller stations only publish the high/low times; for those, Tide Compass draws a smooth interpolated curve between the published highs and lows. The badge on each chart tells you which you’re looking at — interpolated curves are close but slightly less exact between the peaks.
Choosing a time range
- Next 24h — a rolling day starting from right now.
- By date — jump to any calendar day to plan ahead.
- Trip — enter a departure and return time and the chart shades your window, so you can see the tide at both ends of the outing.
Comparing stations
Tides don’t happen at the same moment everywhere — the high at a pass can arrive an hour or more before or after the high up a river. Turn on Compare to overlay several stations on one chart and see how the timing shifts between your launch, your fishing spot, and your takeout.
Don’t forget the weather
Predicted tides assume calm, average conditions. Strong onshore wind can pile water up and push the real level above prediction; persistent offshore wind and high pressure can hold it below. Use the Weather button on any station to check current wind and conditions alongside the tide before you go.