Speed Converter
Convert between km/h, mph, m/s, ft/s, and knots. Three tiers: Quick, Extended with speedometer gauge and SA speed limits, and Professional with acceleration, stopping distance, and Mach number calculators.
Quick Calculator Get a fast estimate
Conversion Result
100 kmh = 62.13721 mph
Metres/second (m/s)
27.77778
Feet/second (ft/s)
91.13444
Knots (kn)
53.99573
How to Use This Converter
Select your source and target speed units, then type a value in either field. South Africa uses km/h for road speeds. Speed limits in SA: 60 km/h in urban areas, 100 km/h on rural roads, 120 km/h on freeways. Knots are used in aviation and maritime navigation.
The Extended Calculator includes a speedometer gauge and SA speed limit reference with Beaufort wind scale. The Professional Calculator adds acceleration, stopping distance, and Mach number calculations.
Need more detail?
Extended Calculator More options, charts, and scenario comparison
Result
74,565 mph
In other units:
74,565mph
33,333ms
64,795knot
0,098mach
SA Speed Limits
| Context | km/h | mph |
|---|---|---|
| Urban roads (SA) | 60 | 37,282 |
| Secondary roads (SA) | 80 | 49,71 |
| National highways (SA) | 120 | 74,565 |
| School zones | 40 | 24,855 |
| Freeway (N1, N2 etc.) | 120 | 74,565 |
Speed Conversion Reference
| Speed | km/h | mph | m/s |
|---|---|---|---|
| City speed limit (SA) | 60 | 37.3 | 16.7 |
| Highway (rural) | 100 | 62.1 | 27.8 |
| Freeway limit (SA) | 120 | 74.6 | 33.3 |
| Sound (air, 20Ā°C) | 1 235 | 767 | 343 |
Need full precision?
Professional Calculator Complete parameters, sensitivity analysis, and detailed breakdown
Speed Conversion (All Scales)
| Unit | Value |
|---|---|
| m/s | 33,333 |
| km/h | 120 |
| mph | 74,565 |
| ft/s | 109,361 |
| Knot (kn) | 64,795 |
| Mach (15Ā°C) | 0,098 |
| Mach (high alt) | 0,113 |
| Speed of light | 1.1119e-7 |
Acceleration Calculator (0ā100 style)
Acceleration
3,472 m/sĀ²
In g-forces
0,354 g
ft/sĀ²
11,392
Stopping Distance Calculator
Total Stopping Distance
130,93 m
Reaction distance
50 m
Braking distance
80,93 m
In feet
429,56 ft
Typical: dry road deceleration = 0.7ā0.8g, wet road = 0.4ā0.5g, SA legal reaction time default = 1.5s.
Mach Number & Escape Velocity Reference
| Reference | m/s | km/h | Mach |
|---|---|---|---|
| Speed of sound (15Ā°C) | 340 | 1 224 | 1.0 |
| Speed of sound (high alt) | 295 | 1 062 | 0,868 |
| Your speed (33,333 m/s) | 33,333 | 120 | 0,098 |
| Commercial aircraft cruise | 250 | 900 | 0.74 |
| Low Earth orbit | 7 800 | 28 080 | 22.9 |
| Earth escape velocity | 11 186 | 40 270 | 32.9 |
| Speed of light | 299 792 458 | 1.08 billion | 880 986 |
Frequently Asked Questions
Multiply km/h by 0.621371 to get mph. Quick mental trick: divide by 8 and multiply by 5. So 120 km/h Ć· 8 Ć 5 = 75 mph.
A knot is one nautical mile per hour. It is used in aviation and maritime navigation because nautical miles are defined by the Earth's geometry (1 nautical mile = 1 arc minute of latitude), making navigation calculations simpler. 1 knot = 1.852 km/h.
The speed of light in a vacuum is approximately 1 079 252 848 km/h, or about 299 792 km/s. This is a fundamental constant used in physics and astronomy.
South African speed limits are: 60 km/h in urban areas, 80 km/h in some suburban zones, 100 km/h on rural roads, and 120 km/h on freeways (motorways). These limits apply unless road signs indicate otherwise.