Unit conversions on the SENASA calculator

The factors used most in the pilot theory exams, with the exact key sequence for the exam calculator and the direction mistake to avoid in each one.

Before you start: two rules

• Decide the direction before typing. The typical mistake is not the factor, it is multiplying when you should divide. Trick: from the large unit to the small one the number must grow (1 NM is 1852 m), so you multiply; from small to large you divide.
• Use the factor in the question. If the question says 1.85 instead of 1.852, or 30 ft/hPa instead of 27, the question wins. The ones in this guide are the usual values.

The Study helper on the calculator recognises these factors when you type them and reminds you of the direction of the conversion.

Distances

• NM → km: × 1.852. 150 NM: 150 * 1.852 = → 277.8 km. See it
• km → NM: ÷ 1.852 (or × 0.54). 277.8 km: 277.8 / 1.852 = → 150 NM. See it
• NM → m: × 1852. For NM → ft, × 6076 (some questions use 6080).
• ft → m: × 0.3048. 2500 ft: 2500 * 0.3048 = → 762 m. See it
• m → ft: ÷ 0.3048 (or × 3.28). 762 m: 762 / 0.3048 = → 2500 ft. See it
• NM → SM (statute miles): × 1.151. SM → km: × 1.609.

Speeds

• kt → km/h: × 1.852, the same as distances. 250 kt: 250 * 1.852 = → 463 km/h. See it
• kt → m/s: × 0.514. m/s → kt: × 1.944.
• kt → ft/min: × 101.3. This is the one that turns a speed into a vertical rate: a 5 % gradient at 120 kt gives 120 * 101.3 * 0.05 = → 607.8 ft/min. See it
• m/s → ft/min: × 196.85.

Mass, volume and fuel

• kg → lb: × 2.205. lb → kg: ÷ 2.205 (or × 0.4536). 1500 lb: 1500 / 2.205 = → 680.27210884 kg. See it
• US gal → L: × 3.785. Imp gal → L: × 4.546. L → US gal: × 0.264.
• Volume → mass: litres × density (SG). 120 L of AVGAS at SG 0.72: 120 * 0.72 = → 86.4 kg. See it
• US gal → kg in one go: gal × 3.785 × SG. 45 US gal at SG 0.72: 45 * 3.785 * 0.72 = → 122.634 kg. See it
• lb of fuel → US gal: ÷ 6 (AVGAS, 6 lb/gal) or ÷ 6.7 (JET A-1, 6.7 lb/gal) unless the question gives another value.

Temperature

• °C → °F: × 1.8 and then + 32. 20 °C: 20 * 1.8 + 32 = → 68 °F. The multiplication comes first and the calculator respects precedence, so this one can be typed straight through. See it
• °F → °C: first − 32, then ÷ 1.8. There is a trap here: if you type 68 - 32 / 1.8 = straight through, the calculator divides before subtracting and gives 50.22. You must press = after the 32: 68 - 32 = / 1.8 = → 20 °C. See it
• °C → K: + 273 (or 273.15). With negative temperatures the sign goes after the number: −40 °C is 40 +/- + 273 = → 233 K. See it
• Speed of sound: LSS (kt) = 38.95 × √(K). At −40 °C: 40 +/- + 273 = √x * 38.95 = → 594.5459465 kt. See it

Pressure

• inHg → hPa: × 33.86. 29.92 inHg: 29.92 * 33.86 = → 1013.0912 hPa. See it
• hPa → inHg: ÷ 33.86 (or × 0.02953).
• hPa → ft in altimetry: × 27 near sea level (some questions give 30). Difference 1013 − 998 = 15 hPa: ( 1013 - 998 ) * 27 = → 405 ft. See it

Time and angles

• Minutes → decimal hours: ÷ 60. Decimal hours → minutes: × 60. 2.35 h: 2.35 * 60 = → 141 min. See it
• Hours and minutes → decimal: 1 h 25 min is 25 / 60 + 1 = → 1.4166666667 h. See it
• Longitude → time: 15° of longitude is 1 hour, that is 4 minutes per degree. 37.5° of difference: 37.5 * 4 = → 150 min. See it
• Radians → degrees: × 57.3. It is the same (approximate) 60 as in the 1 in 60 rule.
• Degrees and minutes of arc → decimal: 43° 30' is 30 / 60 + 43 = → 43.5°. See it

How to practise them

Every conversion on this page can be replayed on the calculator with the «See it» link. The full exam formulas, with the conversions already built in, are in the worked examples, and what each key does is in the complete guide to the calculator.