ETA calculator
Enter your passage distance and average speed over ground to calculate travel time.
Related tools
Worked example
You're planning a 45 nm passage departing at 0800, making 5.5 knots over ground:
- Time = 45 nm ÷ 5.5 kn = 8 hrs 11 min
- Departure 0800 + 8h 11m = ETA 1611
- With tidal stream helping by 0.5 kn → effective 6 kn → ETA 1530
Always add a buffer for variable conditions, and plan to arrive before darkness.
How to use
Enter your passage distance and expected average speed over ground. The calculator gives total travel time. Allow extra time for tides, locks and rest stops.
Time = Distance ÷ Speed
Frequently asked questions
Should I use speed through water or speed over ground?
Always use speed over ground (SOG) for passage planning. Speed through water ignores tidal stream and current — if you're motoring at 6 knots into a 2-knot adverse tide, your SOG is only 4 knots and your passage will take 50% longer than planned.
How do I calculate my ETA with a departure time?
Take the travel time this calculator gives you and add it to your departure time. If the result takes you past midnight, remember to carry over to the next day. For example: depart 2200, travel time 6h 30m → ETA 0430 next day.
What is a nautical mile?
A nautical mile (nm) is 1,852 metres — approximately 1.15 statute miles or 6,076 feet. It's defined as one minute of latitude, which makes it a natural unit for navigation at sea. One knot is one nautical mile per hour.
How do I estimate average speed for passage planning?
For a sailing vessel, use 80–85% of your typical boat speed to allow for light patches and sail changes. For motor vessels, use your normal cruising RPM speed, then subtract an allowance for any adverse tidal stream.