Cruise TAS & Ground Speed Planner
From POH cruise CAS, altitude, temperature and forecast wind: TAS, ground speed each way, and the altitude where this power setting earns its keep.
Same fuel flow, more true speed: altitude pays you in air miles per gallon โ until the climb cost, oxygen rules or the winds aloft take it back. The wind component routinely outweighs everything else on this page.
Formula
โ ๏ธ For flight planning and education only โ verify with your POH/AFM, certified instruments and official sources. Not for primary navigation or airworthiness decisions.
From POH cruise CAS, altitude, temperature and forecast wind: TAS, ground speed each way, and the altitude where this power setting earns its keep.
About Cruise TAS & Ground Speed Planner
Flight-plan ground speeds are built in three honest steps: what the temperature aloft will be (ISA at altitude plus the forecast deviation), what TAS your POH cruise CAS becomes in that air, and what the wind component does to it. This planner chains all three โ taking its inputs in exactly the form forecasts deliver them (ISAยฑ and wind component) โ and adds the efficiency angle: the percentage of free true-speed the altitude is paying you.
How to use Cruise TAS & Ground Speed Planner
- 1Enter โ sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula OAT = ISA(PA) + dev; TAS = CAS/โฯ; GS = TAS + wind component substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Cruise TAS & Ground Speed Planner?
- โInstant, free and private โ every calculation runs in your browser, nothing is uploaded
- โBuilt on the published formula OAT = ISA(PA) + dev; TAS = CAS/โฯ; GS = TAS + wind component with sources cited on the page
- โSame fuel flow, more true speed: altitude pays you in air miles per gallon โ until the climb cost, oxygen rules or the winds aloft take it back. The wind component routinely outweighs everything else on this page.
- โSwitch units, tweak any input and watch every result update live
Frequently asked questions
Where do I get the ISA deviation for planning?+
Winds and temperatures aloft forecasts (FB in the US, GRIB/significant weather elsewhere) publish the actual temperature at altitude; subtract the ISA value (15 ยฐC minus 2 ยฐC per 1,000 ft) to get the deviation. Many aviation apps display 'ISA+3' directly. This tool computes ISA for your altitude internally โ you enter only the deviation.
Why does the same %-power CAS give more TAS higher up?+
Thin air: at constant calibrated airspeed the true speed grows as 1/โฯ โ about 2% per 1,000 ft. Since cruise fuel flow tracks power (roughly constant at a fixed %BHP), the extra true miles are free in fuel terms. POH cruise tables encode this: watch TAS climb down each altitude column at fixed power.
Then why not always cruise as high as possible?+
The climb costs fuel and time the cruise must repay (rule of thumb: it rarely pays on legs under ~50 nm per 5,000 ft of climb), the winds usually strengthen aloft (a headwind grows faster than the TAS does), oxygen rules engage above 12,500 ft cabin, and normally-aspirated engines run out of the power needed to hold the table's CAS. The optimum is a trade, and the wind input here usually decides it.
How accurate is GS = TAS + wind component?+
Exact when the wind is along-track; slightly optimistic when it's quartering, because the crab to hold course spends a sliver of TAS (the cosine of the wind-correction angle). Under 30ยฐ of wind angle the error is below 1%. For serious crosswinds, use our wind-triangle tools in the navigation category for the full vector solution.
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