Nautical Miles (NM)
Statute Miles (SM)
Kilometers (KM)
Knots (kts)
MPH
Km/h
Gallons / Hour
Liters / Hour
Estimated Travel Time:0 hrs 0 mins
Arrival Time (if departing now):–:–
Estimated Fuel Usage:0 Gallons
How to Estimate Boat Travel Time
Planning a trip on the water requires more than just knowing your destination; calculating your Estimated Time of Arrival (ETA) is crucial for safety, fuel management, and daylight planning. Unlike car travel, boat speed can be heavily influenced by sea state, wind, and currents.
The Core Formula
The basic physics of navigation relies on the Time-Speed-Distance formula:
Time = Distance ÷ Speed
However, unit consistency is key. In the maritime world, the standard units are Nautical Miles (NM) for distance and Knots for speed. One knot equals one nautical mile per hour.
Understanding the Units
Nautical Mile (NM): Based on the circumference of the earth. 1 NM ≈ 1.15 Statute Miles (land miles) or 1.852 Kilometers.
Knot (kt): The standard unit of speed on water. If your boat speedometer reads in MPH, you are traveling slower in knots than the number suggests (e.g., 20 MPH is only roughly 17.4 Knots).
Statute Mile (SM): Common in inland lakes and rivers in the US.
Fuel Planning Logic
Calculating travel time allows you to estimate fuel consumption accurately. By knowing your engine's burn rate (Gallons or Liters per Hour) at cruising speed, you can determine total fuel needs using the formula:
Total Fuel = Travel Time (Hours) × Consumption Rate (per Hour)
Safety Tip: Always follow the "Rule of Thirds" for fuel management: 1/3 to get there, 1/3 to get back, and 1/3 in reserve for emergencies.
Factors Affecting ETA
While this calculator provides a mathematical baseline, real-world conditions often add time to the trip:
Currents: Traveling against a 2-knot current effectively reduces your speed by 2 knots.
Sea State: Rough water requires slowing down to maintain comfort and safety.
No-Wake Zones: Slow zones in harbors or channels drastically increase average travel time.
function calculateTravelTime() {
// 1. Get input values
var distanceInput = document.getElementById('travelDistance').value;
var distanceUnit = document.getElementById('distanceUnit').value;
var speedInput = document.getElementById('boatSpeed').value;
var speedUnit = document.getElementById('speedUnit').value;
var fuelRateInput = document.getElementById('fuelRate').value;
var fuelUnit = document.getElementById('fuelUnit').value;
// 2. Validate inputs
if (distanceInput === "" || speedInput === "") {
alert("Please enter both distance and speed to calculate time.");
return;
}
var distance = parseFloat(distanceInput);
var speed = parseFloat(speedInput);
var fuelRate = fuelRateInput === "" ? 0 : parseFloat(fuelRateInput);
if (distance < 0 || speed 0) {
timeString += hours + " hr ";
}
timeString += totalMinutes + " min";
// If less than 1 minute but valid
if (hours === 0 && totalMinutes === 0 && timeInHours > 0) {
timeString = " 0) {
var fuelUnitLabel = fuelUnit === 'gph' ? 'Gallons' : 'Liters';
document.getElementById('displayFuel').innerHTML = totalFuel.toFixed(1) + " " + fuelUnitLabel;
document.getElementById('fuel-row').style.display = 'flex';
} else {
document.getElementById('fuel-row').style.display = 'none';
}
document.getElementById('results-area').style.display = 'block';
}