Tide Calculator: High & Low Tide Times
Pick a coastal station and a date to see NOAA's predicted high and low tide times and heights for that day, the tidal range between them, and whether the Moon phase points to a bigger spring tide or a smaller neap tide.
Fetching tide predictions from NOAA…
Source: NOAA Tides & Currents (CO-OPS), US coasts and Great Lakes stations only. Heights are relative to Mean Lower Low Water (MLLW), the standard US charting datum, not sea level. The curve between readings is a smooth approximation, not itself an official prediction — only the marked points are.
Why tides need real station data, not just a formula
Unlike sunrise or moon phase, which follow predictable astronomical formulas anywhere on Earth, a tide's exact timing and height at a specific place depends heavily on local coastline shape, water depth and how the tidal wave behaves as it moves through bays, inlets and channels. Two ports a short distance apart can have noticeably different tide times. That's why this calculator looks up official predictions for a specific station instead of calculating them from scratch.
The predictions come from NOAA's Center for Operational Oceanographic Products and Services (CO-OPS), built from years of observed water levels at each station and covering US coasts, Hawaii, Alaska and the Great Lakes. Other coastlines aren't covered here, since accurate predictions need the same kind of station-specific historical data for that location.
Reading the day's tides
Most coastal locations get two high tides and two low tides a day (a "semidiurnal" pattern), though some places get only one of each, or an uneven mix, depending on local geography. Heights are given relative to Mean Lower Low Water (MLLW) — the average of the lowest of each day's low tides over a long reference period — which is the standard datum used on US nautical charts, not sea level itself.
The tidal range, the difference between the day's highest and lowest predicted water level, matters for anything sensitive to how far the water moves: launching a boat, checking a tide pool, digging clams, or judging how much beach will be exposed.
Spring and neap tides
The Moon's gravity is the main driver of tides, with the Sun adding a smaller pull of its own. Around new and full moon, the Sun and Moon line up, and their pulls combine to produce a bigger tidal range — a "spring tide." Around the first and last quarter, the Sun and Moon pull at roughly right angles to each other, partly cancelling out and producing a smaller range — a "neap tide." This calculator notes which is more likely for the date you choose, alongside the Moon phase itself.
Frequently asked questions
- What does MLLW mean on a tide chart?
- Mean Lower Low Water — the average of the lowest low tide recorded each day over a long reference period. US nautical charts and NOAA tide predictions measure height relative to this level, not sea level.
- Why does this only cover US locations?
- Accurate tide predictions need years of observed water-level data at each specific station, not just a formula. NOAA freely publishes that data for US coasts, Hawaii, Alaska and the Great Lakes, which is what this calculator uses.
- What is a spring tide?
- A tide with an unusually large range between high and low, which happens around new and full moon when the Sun and Moon's gravitational pull line up and reinforce each other. It has nothing to do with the season of spring.
- What is a neap tide?
- A tide with an unusually small range, happening around the first and last lunar quarter when the Sun and Moon pull at roughly right angles to each other and partly cancel out.
- How accurate are these tide predictions?
- NOAA's predictions are generally accurate to within a few minutes and a fraction of a foot under normal conditions. Storms, strong winds and unusually high or low atmospheric pressure can push actual water levels away from the prediction.