Last reviewed and updated:
Time, speed and distance problems are the backbone of navigation planning and a large share of PPL and CPL ground exam questions. They are simple arithmetic, but under time pressure in the cockpit or the exam room it pays to have a fast, reliable method. This guide covers the formulas, the E6B flight computer method, mental shortcuts and the fuel calculations that go with them.
For a quick answer, use the Time, Speed & Distance Calculator.
The three formulas
- Distance = speed × time
- Time = distance ÷ speed
- Speed = distance ÷ time
Keep the units consistent: distance in nautical miles, speed in knots and time in hours. Convert minutes to hours by dividing by 60, so 45 minutes is 0.75 hours.
Always use ground speed
Time over the ground depends on ground speed, not indicated airspeed. To get it:
- Convert indicated airspeed to true airspeed for altitude and temperature (True Airspeed Calculator).
- Apply the wind to get heading and ground speed (Wind Correction Angle Calculator).
- Use that ground speed for each leg’s time.
The E6B method
On the calculator side of an E6B, the outer scale represents distance (or fuel) and the inner scale represents time, with a speed index arrow (often marked 60) for minutes:
- Set the speed index arrow against the ground speed on the outer scale.
- Find the time in minutes on the inner scale; read the distance opposite it on the outer scale.
- Or find the distance on the outer scale; read the time opposite it on the inner scale.
The scales do not show the decimal point, so always sense-check the order of magnitude. If the answer for a 30-minute leg at 100 kt reads “50”, it is 50 NM, not 5 or 500.
Mental shortcuts
| Ground speed | NM per minute | Quick use |
|---|---|---|
| 60 kt | 1.0 | Minutes = NM |
| 90 kt | 1.5 | Minutes = NM × 2 ÷ 3 |
| 120 kt | 2.0 | Minutes = NM ÷ 2 |
| 150 kt | 2.5 | Minutes = NM × 0.4 |
| 180 kt | 3.0 | Minutes = NM ÷ 3 |
For any speed, find NM per minute by dividing ground speed by 60, then divide the distance by it.
Worked examples
Time. 120 NM at 100 kt: 120 ÷ 100 = 1.2 h = 1 h 12 min.
Ground speed check. Two checkpoints 30 NM apart are passed 15 minutes apart: 30 ÷ 0.25 = 120 kt. If you planned for 110 kt, update your ETA earlier.
Distance. 2 hours at 90 kt: 90 × 2 = 180 NM.
Fuel: the same calculation
Fuel works exactly like distance: fuel used = burn rate × time. A 1 h 12 min leg at 8 US gal/h uses 9.6 gallons. Endurance is fuel on board ÷ burn rate. Remember:
- Add fuel for start, taxi and climb, which the cruise burn rate does not cover.
- Add the legal reserve required by your authority and operator (for example, 30 minutes for VFR day under many ICAO-based rules, but check your country’s regulations).
- For weight and balance, convert fuel volume to weight with the Aviation Fuel Weight Converter.
In-flight revisions
Note the time at each checkpoint on your log. If you reach a checkpoint late, recalculate ground speed and revise the ETA for the remaining legs and your fuel at destination. If you drift off track, the 1 in 60 rule gives the heading correction.
Related tools and guides
- Time, Speed & Distance Calculator
- Aviation Fuel Calculator
- The 1 in 60 Rule Explained
- Student Pilot Ground School Toolkit
For training and general information. Follow your flight school’s procedures and your aviation authority’s fuel and planning rules.
Sources and further reading
- FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25) (navigation chapter, including the flight computer)
- FAA Aviation Handbooks and Manuals (includes the Aviation Weather Handbook, FAA-H-8083-28)
Sources checked November 2026. Rules differ between countries and change over time: for real flights, use the current publications of the authority that applies to you, your aircraft flight manual and your operator’s procedures.