True Airspeed Calculator

Indicated airspeed is what the airspeed indicator reads from dynamic pressure hitting the pitot tube. True airspeed is your actual speed through the surrounding air mass, which is higher at altitude because the thinner air produces less dynamic pressure for the same real speed.

It applies the cockpit rule true airspeed = indicated airspeed times (1 + 0.02 times altitude in thousands of feet). That works out to about 2 percent added for every 1000 feet of pressure altitude, and the tool also reports that exact percentage.

It is a handy approximation that is close enough for rough flight planning at typical piston altitudes. Real true airspeed depends on air density, so both temperature and pressure matter. For dispatch-grade numbers use an E6B or an electronic flight computer that takes outside air temperature.

Yes. Air that is warmer than the standard atmosphere is less dense and pushes true airspeed higher, while colder air makes it lower. This rule of thumb assumes a standard day and ignores temperature entirely, so on a hot day it will slightly underestimate your TAS.

Use pressure altitude, the reading you get with the altimeter set to 29.92 inches of mercury. It strips out local pressure variation, which keeps the estimate consistent regardless of the day's barometric setting.

The output matches whatever speed unit you enter. If you type knots you get knots, and the labels shown read kt. The math is a simple percentage increase, so it works the same for miles per hour or kilometers per hour if you enter those instead.

True airspeed is your speed relative to the air mass. Groundspeed is your speed over the terrain, which also depends on wind. A headwind lowers groundspeed below TAS and a tailwind raises it, so this tool gives TAS, not groundspeed.

No. Both fields require a value, and neither the airspeed nor the altitude can be negative. If a box is empty or holds an invalid or negative number, the tool shows a short prompt instead of a result.

No. The calculation runs entirely in your browser, so your airspeed and altitude entries never leave your device and nothing is stored between visits.