How to read a tide chart

Tide charts look technical, but you only need to understand four things to use one well: when the highs and lows happen, how high they are, what "0 ft" means, and which station the numbers come from. This guide walks through each one with real NOAA data, then shows how surf anglers, surfers and families read the same chart differently.

The parts of a tide chart

Every tide page on TideCharts USA (for example Avalon, NJ or Nags Head, NC) is built from the same NOAA predictions, and every chart has the same building blocks:

• High and low tide times. These are local clock times, already adjusted for daylight saving time. A high tide is the moment the water stops rising; a low tide is the moment it stops falling.
• Heights. The number next to each time ("4.7 ft") is how far the water is predicted to be above the station's MLLW reference level, not how deep the water is.
• The tide curve. The smooth line connects the highs and lows. A steep part of the curve means the water is changing quickly; a flat part near a high or low means it is barely moving.
• The station. Predictions are made for a specific NOAA station, such as Atlantic City (Ocean), NJ. A beach a few miles away, or behind an inlet, can run on a very different schedule (more on that below).

In the chart above, the water at Atlantic City fell to a low just after midnight, rose for about six hours to a 4.7 ft high at 6:25 AM, fell again to a 0.3 ft low at 12:43 PM, and rose to a second high in the evening. The difference between a high and the following low (here about 4.4 ft) is the tide range. A bigger range means more water moving in and out, and usually stronger tidal currents.

What "0 ft" means: MLLW, explained

Tide heights need a starting point. In the US, NOAA uses Mean Lower Low Water (MLLW): the average height of the lower of the two daily low tides, measured over the official 19-year National Tidal Datum Epoch (currently 1983 to 2001). MLLW is also the reference datum for NOAA tide predictions and nautical charts (NOAA tidal datums).

That has a few practical consequences:

• 0 ft is not "no water". It is just an average low. On an ocean beach there is still plenty of water at 0 ft.
• Negative tides are normal. A low tide of -0.5 ft means the water is predicted to drop half a foot below that average low. These "minus tides" tend to show up around new and full moons and expose the most beach, sandbar and jetty rock.
• Heights only compare within one station. At Atlantic City, NOAA's average higher high water (MHHW) is 4.6 ft above MLLW; at Duck Pier, NC on the Outer Banks it is about 3.7 ft (NOAA station datums). So a "4 ft high tide" is ordinary at one place and big at another.

How often tides happen (and why they shift every day)

Along most of the US East Coast the tide is semidiurnal: two high tides and two low tides of roughly similar size each day. The Gulf of Mexico, by contrast, often has just one high and one low a day (NOAA: types of tidal cycles).

The rhythm follows the moon, not the sun. According to NOAA, a "lunar day" lasts 24 hours and 50 minutes, so high tides come about 12 hours 25 minutes apart and it takes about 6 hours 12.5 minutes to go from high to low (NOAA: the lunar day). That is why a high tide at 6:25 AM today will be somewhere around 7:15 AM tomorrow. Real tides wander a bit from these averages, which is why you should read the actual times rather than counting forward.

The size of the tide also cycles. Around new and full moons, ranges get bigger (spring tides); around the quarter moons they get smaller (neap tides). We cover that, plus "king tides", in King tides, spring tides and neap tides explained.

Rising vs. falling: flood, ebb and slack

The direction the water is moving is often more useful than the exact high or low time:

• Rising tide (also called incoming or "flood"): water level going up, from a low toward a high.
• Falling tide (outgoing or "ebb"): water level going down, from a high toward a low.
• Around the turn: near each high and low the curve flattens and the water level barely changes for a while.

Strictly speaking, flood, ebb and slack describe tidal currents (horizontal water movement), while high and low describe the water level. On an open beach the two line up fairly well. In inlets, rivers and back bays they often don't: the current can keep flowing in after the water level has peaked. If you fish or paddle an inlet, check NOAA's tidal current predictions as well as the tide chart.

Every beach page on this site has a "Today's tide windows" box that lists each rising and falling period with its start and end times, so you don't have to work them out yourself.

Pick the right station

This is the most common mistake people make. Tides on the ocean side of a barrier island and in the bay behind it can be hours apart and very different in size. On October 24, 2026, for example, NOAA predicted the morning high tide at Barnegat Inlet, USCG Station, NJ at 6:40 AM, but at Manahawkin Drawbridge, NJ, about 8 miles away in Manahawkin Bay behind Long Beach Island, it was not until 9:36 AM, and the range there was about half as large.

So:

• For an ocean beach, use an ocean station (or a beach page, which picks the nearest suitable station for you and tells you which one it used and how far away it is).
• For a bay, sound, marsh creek or river, use a station on that body of water. Our New Jersey tide stations list includes dozens of back-bay and creek stations.
• If the nearest station is more than a few miles away, treat the times as a guide, and watch the water when you arrive.

The Jersey Shore tide guide and the Outer Banks tide guide show side-by-side comparisons of ocean, inlet and bay stations.

Reading a tide chart for fishing, surfing and the beach

For fishing

Most anglers care about moving water: the hours when the curve is steep. Mark the highs and lows, then look at the rising and falling windows in between and how they overlap with dawn and dusk (our beach pages list first light and last light next to the tides). Bigger ranges usually mean stronger currents. See the best tide for surf fishing for how beach shape changes the answer.

For surfing

Surfers mostly care about tide height at their break: how much water is over the sandbar. Note the height when a session is good, then look for the same height on the chart next time, whether the tide is rising or falling. More in best tide for surfing a beach break.

For beach days, tide pools and kids

Low tide exposes the most beach. Look for a daylight low tide, especially one with a low or negative height. At high tide, especially during spring tides, the dry beach can get narrow, so set up well above the wet sand line. Our beach pages list "This week's lowest predicted tide" for exactly this.

What a tide chart can't tell you

NOAA tide predictions are astronomical: they come from the moon and sun and don't include wind, air pressure, river flow or storm surge. A strong onshore wind or a coastal storm can push water well above the predicted high, and a steady offshore wind can keep it lower. A tide chart also says nothing about waves or rip currents. Before you go:

• Check the live readings on the beach or station page (nearest NDBC buoy waves and water temperature, wind, and NOAA observed water level where the station has a gauge).
• Check the National Weather Service surf zone forecast and rip current information.
• Remember that tide predictions are for planning, not for navigation.

A five-step routine

1. Open the page for your beach, or the closest station on the same body of water.
2. Find today's highs and lows and note the heights. Is the range big or small this week?
3. Look at the rising and falling windows and pick the stage you want (moving water for fishing, a particular height for surfing, a low for beachcombing).
4. Line that window up with daylight, and check wind and waves.
5. When you get there, look at the water. If the beach is behind an inlet or far from the station, adjust.

FAQ

What does MLLW mean on a tide chart?

MLLW stands for Mean Lower Low Water, the average height of the lower of each day's two low tides over NOAA's 19-year National Tidal Datum Epoch (1983 to 2001). It is the zero point for US tide predictions, so a tide of 4.5 ft means 4.5 feet above that average low, not 4.5 feet of water depth.

Why is there a negative tide on the chart?

A negative (minus) tide means the water is predicted to fall below Mean Lower Low Water, the average lower low tide. Minus tides are normal, especially around new and full moons when the tide range is larger, and they expose more beach and sandbar than usual.

How long is it between high tide and low tide?

On a typical East Coast semidiurnal tide it is a little over six hours. NOAA gives the average as about 6 hours 12.5 minutes from high to low, with high tides about 12 hours 25 minutes apart. Actual times vary, so read them from the chart.

Why is high tide about 50 minutes later every day?

Tides follow the moon. A lunar day, the time for a spot on Earth to come back under the moon, lasts about 24 hours and 50 minutes, so each day's tides arrive roughly 50 minutes later than the day before.

Why doesn't the tide at my beach match the chart exactly?

The chart is for a specific NOAA station, which may be miles away or on a different body of water. Tides inside bays and inlets can run hours later than on the ocean. Wind and air pressure also push real water levels above or below the astronomical prediction.

Are tide charts accurate?

NOAA's astronomical predictions are very good for timing and height under normal weather, but they do not include wind, storm surge or river flow. Treat them as a plan, check the weather and live observations, and never use them for navigation.

Sources

• NOAA CO-OPS, Tidal datums (MLLW, MHHW, National Tidal Datum Epoch) and station datums for 8534720 and 8651370.
• NOAA National Ocean Service, Frequency of tides: the lunar day and Types of tidal cycles.
• NOAA CO-OPS tide predictions for stations 8534720, 8533615 and 8533935 (October 24, 2026).
• NOAA Tidal current predictions; National Weather Service Rip current safety.