ETA Formula (Estimated Time of Arrival)
Calculate estimated time of arrival using distance, speed, and departure time.
Essential for navigation, shipping, flight planning, and logistics.
The Formulas
ETA = Departure Time + T
The ETA (Estimated Time of Arrival) formula is one of the most practical calculations in navigation, logistics, and everyday travel. It answers the simple but important question: when will I arrive?
You need two things: how far you are going (D), and how fast you are moving (S). Divide distance by speed to get travel time, then add it to your departure time to get the ETA.
Variables
| Symbol | Meaning | Unit |
|---|---|---|
| ETA | Estimated Time of Arrival | hh:mm (clock time) |
| T | Travel time | hours (decimal) |
| D | Distance to destination | km, miles, or nautical miles |
| S | Speed (average, or expected) | km/h, mph, or knots |
Converting Decimal Hours to hh:mm
The result of D/S is in decimal hours (e.g., 1.75 hours). To convert to hours and minutes: multiply the decimal part by 60.
Example: 1.75 hours = 1 hour + (0.75 × 60) = 1 hour 45 minutes.
Example 1 — Ship Navigation
A cargo ship departs port at 08:30. Distance to destination: 240 nautical miles. Average speed: 18 knots.
T = 240 / 18 = 13.33 hours
0.33 hours × 60 = 20 minutes → T = 13 hours 20 minutes
ETA = 08:30 + 13:20 = 21:50
ETA = 21:50 (same day)
Example 2 — Commercial Flight
A flight covers 1,450 km at a cruise speed of 850 km/h. Departure time: 14:15.
T = 1,450 / 850 = 1.706 hours
0.706 hours × 60 ≈ 42 minutes → T = 1 hour 42 minutes
ETA = 14:15 + 01:42 = 15:57
ETA = 15:57
Example 3 — Road Trip with a Stop
Road trip: 480 km at 100 km/h. Depart at 09:00. One 30-minute fuel stop.
T = 480 / 100 = 4.80 hours = 4 hours 48 minutes
Add 30 minute stop: total time = 5 hours 18 minutes
ETA = 09:00 + 05:18 = 14:18
ETA = 14:18
Time Zone Considerations
Always convert your calculated ETA to the local time at your destination. Long flights and ocean passages can cross multiple time zones. A flight from New York (UTC-5) to London (UTC+0) that takes 7 hours departing at 20:00 EST arrives at 03:00 EST — but local time in London is 08:00 GMT.
Ships and aircraft typically track time using UTC (Coordinated Universal Time) for consistency, then convert to local time only for port arrival reporting or passenger information.
ETA vs. ETD vs. ETE
- ETA — Estimated Time of Arrival (clock time at destination)
- ETD — Estimated Time of Departure (when you leave)
- ETE — Estimated Time En Route (total journey duration = T)
When to Use It
Use the ETA formula when:
- Planning road trips or checking if you will arrive before a deadline
- Maritime navigation and voyage planning for commercial vessels
- Aviation flight planning — every filed flight plan includes an ETE and ETA
- Logistics and supply chain management for delivery scheduling
- Emergency services estimating response time based on location and speed
- Racing and competition — calculating pace needed to achieve a target finish time