How to read a tide table
Four numbers, two highs, two lows. Everything else is fluff.
The four numbers that matter
A tide table looks like a wall of digits, but a day really only gives you four: the time and height of each high and each low. Learn those and you can read any station on earth.
station harbor mouth · 2026-09-19 high 06:42 2.4 m low 13:08 0.3 m high 19:11 2.7 m low 01:36 0.4 m (+1 day)
Height is measured from chart datum
Every height is measured up from chart datum — the lowest level your charts are drawn to. Add your draft to the charted depth and compare against the tide height to know if you clear the bar.
The two high tides are not equal
Notice the morning and evening highs differ. That's the diurnal inequality — the moon's orbit is tilted, so one tide of the pair is almost always bigger. Plan the shallows for the bigger one.