How to Read a Tide Chart

A tide chart can look confusing the first time you see one.

There are times, numbers, high and low labels, curved lines, water heights, and sometimes abbreviations such as MLLW that seem designed for sailors rather than ordinary beachgoers.

But the basic information is actually simple.

A tide chart tells you when the water is expected to reach high and low tide and how high or low the predicted water level will be relative to a local reference point.

Once you understand those pieces, you can use tide charts to plan beach walks, tide-pool visits, shelling, fishing, photography, kayaking, and ordinary beach days.

Here is how to read one.

🌊 What Is a Tide Chart?

A tide chart is a prediction of how ocean water levels will rise and fall at a particular coastal location.

Depending on the source, you may see the prediction presented as a graph, a table, or both.

On a graph, time runs across the horizontal axis while predicted water level is shown vertically. The peaks represent high tides and the valleys represent low tides.

A table gives the same basic information in another format, usually listing the date, time, predicted height, and whether the event is a high or low tide.

NOAA Tide Predictions provides both graphical plots and tabular listings for thousands of U.S. tide stations.

⏰ Start With the Time

The first thing most beach visitors want to know is when high tide and low tide will happen.

A tide table might look something like this:

Time	Predicted Tide	Type
6:15 a.m.	0.4 ft	Low
12:30 p.m.	5.2 ft	High
6:45 p.m.	0.8 ft	Low

This is only an example, but reading it is straightforward.

At 6:15 a.m., the water is predicted to reach a low point.

From there, the water rises until approximately 12:30 p.m., when it reaches high tide.

It then begins falling again toward the next low tide around 6:45 p.m.

You do not need to arrive at the exact minute printed on the chart.

The water is gradually changing throughout the hours between those high and low points.

🌊 What Does the Tide Height Mean?

The number beside each high or low tide tells you the predicted water level relative to a reference level called a tidal datum.

This is where tide charts can become confusing.

If the chart says:

High tide: 5.2 feet

that does not mean the ocean will be 5.2 feet deep where you are swimming.

It means the predicted water level at that tide station will be 5.2 feet above the reference datum used for that chart.

NOAA explains that tidal datums are reference levels based on long-term water-level observations at particular locations. They allow water heights to be measured consistently.

For an ordinary beach visit, you generally do not need to calculate the datum yourself.

What matters most is comparing the high and low numbers to understand how much the water level is expected to change.

📏 What Does MLLW Mean?

On many U.S. tide charts, you will see MLLW, which stands for Mean Lower Low Water.

This is a commonly used reference datum for U.S. coastal tide predictions and nautical charts.

In locations that experience two low tides during a tidal day, one low tide is often lower than the other. MLLW is based on the average of those lower low-water levels over a long observation period.

A tide prediction of 0.5 feet MLLW therefore means the water is predicted to be half a foot above that reference level.

A negative tide height can also appear.

For example:

Low tide: -0.7 feet

does not mean the ocean somehow has negative depth.

It means the predicted water level will fall 0.7 feet below the chart’s reference datum.

Negative low tides can be particularly interesting for tide pooling and beach exploration because unusually low water may expose parts of the intertidal zone that are normally submerged.

📈 How to Read a Tide Graph

A tide graph makes the daily rise and fall of the water easy to visualize.

Time moves from left to right.

Water level moves up and down.

When the curve climbs, the tide is rising.

When the curve reaches a peak, you are at approximately high tide.

When the curve descends, the tide is falling.

When it reaches a valley, you are at approximately low tide.

NOAA’s graphical tide predictions use a curve between predicted high and low values to approximate how the water level changes during the intervening hours.

The graph is especially useful if your activity does not depend on the exact moment of high or low tide.

For example, if you want a broad beach for an afternoon walk, you can look at the curve and see whether the water will generally be falling or rising while you are there.

⬆️ What Does a Rising Tide Mean?

A rising tide means the water is moving toward the next high tide.

You may also hear this called an incoming tide.

As the tide rises, the shoreline generally moves farther inland.

That can mean less exposed beach, deeper water near shore, submerged tide pools, and changing currents around rocks, channels, inlets, and sandbars.

If you set up chairs near the water during low tide, a rising tide is important because the ocean may eventually reach your spot.

If you are exploring around cliffs, rocky headlands, or tidal islands, a rising tide deserves even more attention because it can cut off your return route.

⬇️ What Does a Falling Tide Mean?

A falling tide means the water is moving toward the next low tide.

It is also called an outgoing tide.

As the tide falls, more shoreline usually becomes exposed.

That can make the falling tide particularly useful for beachcombing, long walks, tide-pool exploration, and photography.

The newly exposed sand may reveal shells, tidal pools, rocks, sandbars, and other features that were underwater a few hours earlier.

But outgoing water can also contribute to strong currents in channels and inlets.

Low tide should never be treated as automatically safe swimming conditions.

↕️ What Is Tidal Range?

The tidal range is the difference between high tide and low tide.

Suppose your chart shows:

High tide: 5.5 feet

Low tide: 0.5 feet

The tidal range is about 5 feet.

That means the predicted water level changes by roughly five feet between those two tidal extremes.

A beach with a large tidal range may look dramatically different between high and low tide.

A beach with a small tidal range may change much less.

This is why tide height matters in addition to the high- and low-tide times.

Two beaches can both be approaching low tide while experiencing very different changes in shoreline exposure.

🌙 Why Are There Sometimes Two High Tides and Two Low Tides?

Many coastal locations experience two high tides and two low tides during a lunar day.

A lunar day lasts approximately 24 hours and 50 minutes, which is slightly longer than a normal 24-hour day.

In a typical semidiurnal tidal pattern, successive high tides occur roughly 12 hours and 25 minutes apart, with approximately six hours between a high and the following low.

That is why the tide does not occur at exactly the same clock time every day.

Tomorrow’s high tide will generally occur later than today’s.

However, not every coastline follows the same pattern.

Some locations experience only one high and one low tide each day, while others have two tides of noticeably different heights.

Always use the tide chart for the specific coast you are visiting.

🌊 Why Are the Two High Tides Different Heights?

If your chart shows two high tides on the same day, you may notice that they are not identical.

The same can happen with the two low tides.

For example, a chart might show one high tide at 4.8 feet and another at 5.6 feet.

Likewise, one low tide might be 1.1 feet while the next falls to 0.2 feet.

This is normal at many locations.

The tidal pattern is influenced by geography, the positions of the moon and sun, and the shape and depth of the surrounding coastline and seafloor.

When planning something such as tide pooling, the lower of the day’s low tides may be much more interesting than the higher low tide.

🐚 Which Number Matters Most for Beachcombing?

For beachcombing, pay attention to both the time of low tide and the predicted low-tide height.

A lower predicted tide generally exposes more shoreline than a higher low tide at the same beach.

Suppose Monday’s low tide is 1.2 feet and Tuesday’s is -0.3 feet.

Tuesday’s low tide may expose considerably more of the intertidal zone.

That does not guarantee better shelling, because waves, recent storms, local geography, and other factors matter too.

But it tells you that more shoreline is expected to be exposed.

A falling tide leading toward a low tide can also be enjoyable because fresh areas continue appearing as you walk.

🦀 Which Number Matters for Tide Pools?

Tide-pool visitors should look for the lowest low tide that occurs during daylight hours.

A very low tide at 2 a.m. may not be useful for ordinary sightseeing.

A somewhat higher low tide at 11 a.m. may provide a much better opportunity simply because you can explore safely in daylight.

Try to arrive before the predicted low point.

That gives you time to explore as the water continues receding and then begin heading back before the incoming tide covers the area again.

Never remain in a location where a rising tide could trap you against cliffs, rocks, or headlands.

🌅 How to Use a Tide Chart for Photography

Tide charts are especially useful for coastal photography because the tide dramatically changes the foreground.

A low tide can expose wet reflective sand, rock formations, tide pools, sand ripples, and other textures.

A high tide creates a more water-dominated scene.

Suppose sunset occurs around 7 p.m.

If low tide is at 6:30 p.m., you might expect a broad area of wet sand around sunset.

If high tide occurs at 7 p.m., the water may reach much farther up the beach.

Neither is necessarily better.

The chart simply helps you anticipate what the landscape may look like when the light is best.

🐦 How to Use a Tide Chart for Bird Watching

Tides strongly influence where many coastal birds feed.

Falling and low tides can expose mudflats, wet sand, tidal flats, and shallow feeding areas used by shorebirds.

As the tide rises, those feeding areas disappear and birds may become concentrated onto smaller patches of remaining shoreline or move toward roosting areas.

That means a bird watcher might use the tide chart very differently from a swimmer.

Instead of simply asking, “When is low tide?” you might ask, “Will the tide be falling during the first two hours after sunrise?”

A chart makes that easy to see.

🎣 How to Read a Tide Chart for Fishing

Anglers often care about whether the water is moving as much as they care about the exact time of high or low tide.

A tide chart lets you see when water is rising and falling and when it approaches the turning points around high and low tide.

The ideal period depends on the species, location, habitat, season, and fishing method.

There is no universal rule that high tide or low tide is always best.

Local fishing reports, tackle shops, and guides can help you interpret how the tide affects a particular beach, inlet, pier, or bay.

The tide chart provides the timing.

Local knowledge tells you what that timing means for the fish.

🕐 Make Sure You’re Looking at the Correct Time Zone

This is an easy detail to overlook.

NOAA Tide Predictions lets users display times in local time with daylight-saving adjustments, local standard time without daylight-saving adjustments, or GMT.

For ordinary beach planning, local time adjusted for daylight saving when appropriate is usually the easiest setting.

Check the label beside the tide times before assuming 7:15 means 7:15 on your watch.

This matters especially if you are looking at a chart created for sailors, downloading data, or using a website with configurable time-zone settings.

📍 Use the Correct Tide Station

Tide predictions are location-specific.

Do not search for the tide in an entire state and assume the result applies equally everywhere along the coast.

NOAA provides predictions for more than 3,000 U.S. tide-prediction locations. Users can search by station name, station ID, or latitude and longitude.

Choose the closest appropriate station to your beach.

At many ordinary beach destinations, a nearby station gives a useful estimate.

But around complicated bays, rivers, inlets, islands, and estuaries, tide timing and height can differ noticeably over relatively short distances.

If a park, refuge, marina, or local authority recommends a particular tide station, use it.

🗺️ What Is a Harmonic vs. Subordinate Tide Station?

You may encounter these terms when using NOAA’s tide system.

A harmonic station has enough long-term tidal data for NOAA to generate predictions directly using that station’s tidal characteristics.

A subordinate station uses adjustments based on a nearby reference station.

For an ordinary beach visitor, you do not need to understand the mathematics behind this.

The important thing is that NOAA’s system accounts for location-specific differences rather than simply applying one tide schedule to an entire coastline.

🌕 What Do Especially High and Low Tides Mean?

As you look across several days, you may notice that the high tides gradually get higher and the low tides get lower.

Then the pattern reverses.

This is partly connected to the positions of the moon and sun.

Around new and full moons, spring tides produce a larger tidal range—generally higher high tides and lower low tides.

Around the first- and third-quarter moons, neap tides generally produce a smaller tidal range.

Spring tides have nothing to do with the spring season.

They occur throughout the year.

If you are looking for unusually low water for tide pooling, shelling, or photography, the larger tidal ranges around spring tides can be particularly interesting.

➖ What Does a Negative Tide Mean?

Negative tide heights often surprise beginners.

Imagine your chart says:

Low tide: -1.0 ft

The beach is not losing a foot of ocean.

The prediction simply places the water level one foot below the chosen reference datum.

At locations where negative tides occur, they can expose unusually large sections of the intertidal zone.

Tide-pool enthusiasts and coastal photographers often pay special attention to them.

But very low tides can also expose slippery rocks, mud, reefs, and other hazards.

Extra exposed shoreline is not automatically easy or safe terrain.

⏱️ When Should You Arrive for Low Tide?

You usually do not need to arrive at the exact low-tide minute.

For tide pooling or beachcombing, arriving before low tide is often more useful.

If low tide is predicted for noon, arriving around late morning allows you to explore while the water is still receding.

You can then begin returning as the tide turns and starts rising.

How much earlier you should arrive depends on the activity, terrain, tidal range, and location.

At a broad sandy beach, timing may be flexible.

At a tide-pool area accessible only during low water, follow local guidance carefully.

🌊 Does High Tide Happen All at Once?

No.

The tide gradually rises toward high water, reaches a turning point, and then begins to fall.

The exact high-tide time identifies the predicted peak.

It does not mean the ocean suddenly jumps upward at that moment.

Likewise, low tide marks the predicted lowest point rather than an abrupt drop.

When planning a beach activity, think in terms of a moving cycle rather than isolated high and low events.

The curve on a tide graph makes this especially easy to understand.

🌦️ Tide Predictions Are Not the Same as Actual Water Levels

A tide chart is a prediction.

Actual water level can differ because weather influences the coast too.

Strong winds can push water toward or away from shore.

Atmospheric pressure, storms, waves, river flow, and other conditions can also affect observed water levels.

That means the predicted high tide is not a guarantee that the ocean will reach one exact line on the beach.

During storms, coastal flooding, or unusual weather, rely on current water-level observations and official coastal warnings in addition to ordinary astronomical tide predictions.

🌊 A Tide Chart Does Not Tell You Whether Swimming Is Safe

This distinction is extremely important.

A tide chart tells you about predicted water level.

It does not tell you:

whether rip currents are dangerous,

whether waves are too rough,

whether thunderstorms are approaching,

whether the beach has a red flag,

or whether water quality is safe.

High tide is not automatically dangerous.

Low tide is not automatically safe.

Before swimming, check the surf-zone forecast, rip-current risk, weather, beach-warning flags, and lifeguard advice separately.

Use the tide chart as one part of the conditions picture.

📱 Where to Find an Official Tide Chart

For U.S. beaches, NOAA Tides & Currents is one of the best places to start.

NOAA Tide Predictions allows you to search for a station and view predictions in either a graph or table.

You can select your dates, switch between feet and meters, choose the time zone, change between a 12-hour and 24-hour clock, and—at appropriate stations—choose the tidal datum used for the displayed heights.

For a normal beach outing, keep things simple.

Select the nearest appropriate station.

Use local time.

Look at the high and low times.

Compare the predicted heights.

Then decide what part of the tidal cycle best fits what you want to do.

🧭 A Simple Example

Imagine you are planning a beach visit and the chart says:

6:30 a.m. — Low tide — 0.2 ft

12:45 p.m. — High tide — 5.1 ft

7:00 p.m. — Low tide — 0.7 ft

If you want to beachcomb early in the morning, the 6:30 low tide looks promising.

If you arrive at 9 a.m., the tide will already be rising toward the midday high.

If you set your chairs close to the water at 9 a.m., expect the waterline to move toward you through the morning.

By early afternoon, the water should be close to its highest predicted level.

Later in the afternoon, it begins receding again toward the evening low.

That is essentially all you need to understand for most ordinary beach planning.

✅ The Five Things to Read on a Tide Chart

When you open a tide chart, identify five things.

First, make sure you have the right location.

Second, confirm the date and time zone.

Third, look at the high- and low-tide times.

Fourth, compare the predicted tide heights.

Finally, determine whether the water will be rising or falling during the hours you plan to be there.

If you understand those five pieces, you can use almost any basic tide chart.

🏖️ Reading a Tide Chart Doesn’t Have to Be Complicated

For most beach visitors, you do not need to understand oceanography to use a tide chart.

Find the nearest appropriate station.

Look for the day’s high and low tides.

Read the times.

Compare the heights.

Follow the curve to see whether the water will be rising or falling during your visit.

Then use that information according to your plans.

Low tide may help you find tide pools and a broader beach.

A falling tide may be excellent for beachcombing.

A rising tide tells you not to leave your chairs too close to the water.

An unusually low predicted tide may expose parts of the coast you rarely see.

And an incoming tide around cliffs or rocky headlands may tell you it is time to head back.

The tide chart does not tell you everything about the ocean.

It does tell you something extremely useful:

where the water is expected to be—and which direction it is going next.

Once you understand that, those complicated-looking numbers and curves become one of the simplest tools for planning a better beach day.