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Aviation calculators/Flight planning/Point of equal time
FLIGHT PLANNING

Point of equal time calculator

Find the place along a single route segment where the modeled time to return to departure equals the time to continue to destination.

Instant resultsGround speeds in knotsNo account needed

Route assumptions

Live calculation

Enter planned ground speeds for the two directions. Speeds are knots, distances nautical miles, and endurance hours.

NM
Along the planned route, not straight-line distance.
kt
Toward the destination at the applicable flight condition.
kt
Back toward departure at the applicable flight condition.
Use forecast winds and appropriate diversion performance to establish the two ground speeds. Calculate ground speed →

Your equal-time point.

LIVE RESULTS
Point of equal time from departure272.7 NM

At this point, return and continue take the same modeled time.

Distance to destination327.3 NM
Time either way from PET2 h 44 min
Time from departure to PET2 h 16 min
THE METHOD

Balance return and onward time.

The distance back divided by back ground speed equals the distance onward divided by forward ground speed. A headwind or slower diversion speed shifts the equal-time point away from the geometric midpoint.

The formulaDistance from departure = route distance × GS back / (GS back + GS onward)

Ground speed must be positive in both directions. Knots and nautical miles produce times in hours. Calculations use full precision; displayed distances round to one decimal and times to the nearest minute.

WORKED EXAMPLE

A route in numbers.

For a 600 NM route, 120 kt onward and 100 kt back, the equal-time point is 272.7 NM from departure and 327.3 NM from destination. Either diversion takes about 2 h 44 min from that point.

Method reference: CASA Part 141 sample operations manual, sections 2B5.2.3–2B5.2.4. This site applies its equations to a simplified route between departure and destination.

Explore the point of no return calculator →

A few common questions

Is the equal-time point halfway along the route?+

Only when the ground speeds in both directions are equal. Different winds or flight conditions shift it.

Does PET tell me which airport to choose?+

No. It compares modeled flying times between the two named endpoints. It does not assess fuel, alternate suitability or operational constraints.

Understand the limits of this estimate.

Equal time does not mean equal fuel or equal safety. Destination and departure suitability, diversion routes, altitude, varying winds, weather and aircraft performance must be assessed separately. Verify current official information, required reserves and approved aircraft documentation.