All conversions use international foot (1 ft = 0.3048 m exactly). For State Plane coordinate work AvPlot uses US Survey Feet — difference is negligible for planning (2 ppm).
FEET (ft)
↔
METERS (m)
FEET (ft)
↔
NAUTICAL MILES (NM)
STATUTE MILES (SM)
↔
NAUTICAL MILES (NM)
STATUTE MILES (SM)
↔
METERS (m)
STATUTE MILES (SM)
↔
KILOMETERS (km)
NAUTICAL MILES (NM)
↔
METERS (m)
NAUTICAL MILES (NM)
↔
KILOMETERS (km)
Feet
Meters
Common Use
3,000
914
Small GA
5,000
1,524
Medium GA
7,000
2,134
Regional
8,000
2,438
Commercial
10,000
3,048
Commercial
12,000
3,658
Large hub
16,000
4,877
Long haul
Exact factors: 1 international ft = 0.3048 m; 1 NM = 1,852 m; 1 SM = 1,609.344 m. Length conversions are exact mathematical relations, not AC-governed.
Speed
Approach speed categories (AAC) are defined by threshold crossing speed in knots.
KNOTS (kt)
↔
MILES PER HOUR (mph)
KNOTS (kt)
↔
KILOMETERS PER HOUR (km/h)
MILES PER HOUR (mph)
↔
KILOMETERS PER HOUR (km/h)
Category
Speed Range
Notes
AAC-A
< 91 kt
< 105 mph
AAC-B
91–120 kt
105–138 mph
AAC-C
121–140 kt
139–161 mph
AAC-D
141–165 kt
162–190 mph
AAC-E
≥ 166 kt
≥ 191 mph
Speed ranges are threshold crossing speeds (Vat) per AC 150/5300-13B.
Area
Useful for RSA, RPZ, and OFA area calculations and land acquisition estimates.
SQUARE FEET (sq ft)
↔
ACRES (ac)
SQUARE FEET (sq ft)
↔
SQUARE METERS (sq m)
ACRES (ac)
↔
SQUARE METERS (sq m)
ACRES (ac)
↔
HECTARES (ha)
Surface
Typical Size
Acres
RSA (ADG III)
400×2,000 ft
18.4 ac
RPZ (visual, AAC A/B)
1,000×500×700 ft
13.774 ac
RPZ (< 3/4-mile, all)
2,500×1,000×1,750 ft
78.914 ac
1 city block
~100,000 sq ft
2.3 ac
Convenience reference — area conversions are exact (1 acre = 43,560 sq ft; 1 ha = 10,000 sq m). RPZ dimensions and acreages per AC 150/5300-13B Appendix G; RSA and city-block figures are approximate.
Slope
FAA surface slopes are expressed as ratios (20:1 = 20 ft horizontal per 1 ft vertical). Runway grades use percent.
RATIO (X:1)
Enter X where slope = X:1 (horizontal:vertical)
PERCENT GRADE (%)
DEGREES (°)
Obstacle Clearance Surfaces define the required clearance slopes above which no obstacles may penetrate on the approach and departure ends of a runway. Used for ALP design and obstruction evaluation per AC 150/5300-13B Change 1.
SURFACE
OCS #
RATIO
PERCENT
DEGREES
Visual Approach
OCS 1
20:1
5.000%
2.862°
NPI Approach
OCS 2
34:1
2.941%
1.685°
APV Approach
OCS 3
34:1
2.941%
1.685°
Precision CAT I Approach
OCS 4
50:1
2.000%
1.146°
Precision CAT II/III Approach
OCS 5
50:1
2.000%
1.146°
Visual Departure
OCS 6
20:1
5.000%
2.862°
Instrument Departure
OCS 7
40:1
2.500%
1.432°
Source: AC 150/5300-13B Change 1
Click any row to populate slope inputs.
Part 77 imaginary surfaces define the airspace around airports used to evaluate obstructions to air navigation. These surfaces differ in purpose from OCS — Part 77 governs obstruction evaluation while OCS governs ALP design clearances.
SURFACE
RATIO
PERCENT
DEGREES
Transitional Surface
7:1
14.286%
8.130°
Conical Surface
20:1
5.000%
2.862°
Approach Surface — Visual
20:1
5.000%
2.862°
Approach Surface — NPI
34:1
2.941%
1.685°
Approach Surface — Precision (inner, first 10,000 ft)
50:1
2.000%
1.146°
Approach Surface — Precision (outer, next 40,000 ft)
40:1
2.500%
1.432°
Source: 14 CFR Part 77 — Subpart C
Click any row to populate slope inputs.
Temperature
Airport elevation and temperature affect required runway length calculations.
FAHRENHEIT (°F)
↔
CELSIUS (°C)
CELSIUS (°C)
↔
KELVIN (K)
FAHRENHEIT (°F)
↔
KELVIN (K)
Condition
°F
°C
K
ISA standard
59°F
15°C
288.15 K
ISA + 10°C
77°F
25°C
298.15 K
ISA + 15°C
86°F
30°C
303.15 K
ISA + 20°C
95°F
35°C
308.15 K
Water freezing
32°F
0°C
273.15 K
Water boiling
212°F
100°C
373.15 K
ISA (International Standard Atmosphere) = 15°C at sea level. Runway length requirements increase approximately 1% per 1,000 ft elevation and 1% per 10°F above standard temperature.
Pressure
Altimeter settings are reported in inHg in the US and hPa internationally. Standard sea level pressure is 29.92 inHg = 1,013.25 hPa.
INCHES OF MERCURY (inHg)
↔
HECTOPASCALS (hPa) = MILLIBARS (mb)
hPa and mb are equivalent (1 hPa = 1 mb)
Condition
inHg
hPa
Standard sea level
29.92
1,013.25
High pressure
30.50
1,032.85
Low pressure
29.00
982.05
Lowest recorded
25.69
870.00
Conversion factor: 1 inHg = 33.8638816 hPa. Standard sea-level pressure (29.92 inHg = 1,013.25 hPa) per ICAO Standard Atmosphere.
Results shown to 4 significant figures. All conversion factors are exact or per international standards.