IAS to TAS Calculator

IAS → TAS Conversion

Appendix “Conversion table for IAS to TAS calculations”. Unit switches (kt/km/h, m/ft), out-of-table formula, quick chart, Excel export.

Result

Formula used

TAS vs Altitude (at current IAS & VAR)

Ranges: metres 0–7 500 m, feet 0–24 000 ft. Formula is applied for values not listed in the appendix tables. Non-profit educational tool.

Ground Speed from TAS & Wind

Compute GS when flying a given track, accounting for wind. Outputs also drift (WCA), head/tailwind and crosswind components.

Ground Speed (GS)
— kt
— km/h
Drift (WCA)
— °
Crab toward wind source
Heading to fly
— °T
= TRK ± WCA
Head/Tailwind
— kt
Crosswind
— kt
Show formula & notes

Let θ = WD − TRK (degrees, wind from). Convert to radians for trig.
R = WS·sinθ (crosswind), H = WS·cosθ (headwind >0).
WCA = asin(R/TAS) if |R| ≤ TAS, otherwise track cannot be maintained.
GS = TAS·cos(WCA) − H.

  • Units: 1 kt = 1.852 km/h.
  • All angles are TRUE; apply magnetic variation as required.
  • “Heading to fly” is TRK adjusted by WCA toward the wind source.

Required Vertical Speed

Compute the vertical speed needed to meet a required climb/descent gradient (PDG) for SIDs or Missed Approaches.

Required vertical speed
— ft/min
— m/s
► Compute PDG from two altitudes and a distance
PDG: — % (climb/descent)
PDG = 100 × (ΔAltitude / Horizontal distance). Sign indicates climb (B>A) or descent (B<A). The required VS above uses this PDG with the Ground Speed you set.
Show formula & notes

VS: VSfpm = GSkt × 101.2686 × (PDG/100)
PDG from A,B,Distance: PDG% = 100 × (Δh / s) where Δh and s are in the same length units.

  • 1 kt = 1.852 km/h; 1 NM = 1.852 km; 1 ft = 0.3048 m.
  • Input boxes accept comma or dot as decimal separators.

Equivalent Approach Obstacle Height (ha)

Compute ha for multiple obstacles. For side-surface penetrations (PANS-OPS §4.4.3.2) enable “Side surface” and provide h′ma.

ID hma
Side surface
Use h′ma instead 		h′ma x (range) xz ha result
Controlling obstacle (highest ha)
—
Final height: —
Height loss / altimeter margin
Margin: —
Table II-1-1-2 values. Cat E: use equation (not tabulated).
Show formula & notes

Main formula (final/Z/ground): h_a = (h_ma·cot Z + (x_z + x)) / (cot Z + cot θ)

Side-surface variant (§4.4.3.2): use h′_ma in place of h_ma → h_a = (h′_ma·cot Z + (x_z + x)) / (cot Z + cot θ)

  • Angles θ and Z in degrees (elevation). x is negative after threshold. Typical xz=900 m (fixed-wing) or 700 m (Cat H).
  • All heights follow “Heights unit”; all distances follow “Distances unit”.