Many chart plotters will automatically calculate your Estimated Time of Arrival (ETA) and display the remaining time to reach your destination (often called "Time to Waypoint" or "Time to Go") once you've entered your destination or route.
Important considerations
1 knot = 1 nautical mile per hour
D ÷ S = Time (in decimals of an hour)
To convert the decimals into minutes x 60
An example:
How long will it take to travel 3.2 nautical miles at 10 knots?
3.2 ÷ 10 knots = 0.32 x 60 = 19.2 minutes
Fuel Consumption: (Power Vessels)
Dependant on your speed, engine type, horsepower etc.
But a good rule of thumb is 1/3 out, 1/3 back and 1/3 in reserve