Speed Converter — km/h, mph, m/s & Knots for Roads, Weather & Sports

Speed limits, sports records, and spec sheets all use different units

A speed limit sign in Bangladesh reads 80 km/h. A weather report mentions a cyclone with winds at 150 km/h. An aircraft cruises at 900 km/h. A ship logs 20 knots. An American car spec lists 0–60 mph in 5.2 seconds. These are all expressing speed — but the units vary by country and context, and converting between them requires knowing the right factors.

Speed Units in Daily Use

Kilometres per hour (km/h): Standard for road traffic in most countries including Bangladesh. 1 km/h = 1,000m ÷ 3,600s = 0.2778 m/s.

Miles per hour (mph): Used in the US, UK, and some other countries. 1 mph = 1.609 km/h = 0.447 m/s.

Metres per second (m/s): The SI unit for speed. Used in physics and engineering. 1 m/s = 3.6 km/h.

Knots: Used in maritime and aviation contexts. 1 knot = 1 nautical mile per hour = 1.852 km/h = 1.151 mph.

Feet per second (ft/s): Used in some US engineering contexts. 1 ft/s = 0.3048 m/s = 1.097 km/h.

Key Conversion Factors

How to Use the Speed Converter on sadiqbd.com

1. Enter the speed value
2. Select the source unit — km/h, mph, m/s, knots, ft/s
3. Read the converted equivalents

Real-World Speed Conversions

Road trip on an international route

Driving in India where speed limits are in km/h, then crossing into a country with mph signage:

80 km/h × 0.621 = 49.7 mph — just under 50 mph

100 km/h = 62.1 mph 120 km/h = 74.6 mph

Sports performance

A cricket bowler clocked at 145 km/h. In mph (for international comparison):

145 × 0.621 = 90.1 mph — fast bowling territory, on par with international fast bowlers.

A sprinter runs 100m in 10.5 seconds. Average speed:

100m ÷ 10.5s = 9.52 m/s 9.52 × 3.6 = 34.3 km/h 34.3 × 0.621 = 21.3 mph

Usain Bolt's peak speed during the 100m world record was approximately 44.7 km/h (27.8 mph) — showing how professional sprinters sustain much higher peak speeds than the 100m average suggests.

Cyclone and weather warnings

Bangladesh Meteorological Department issues warnings with wind speeds in km/h. Converting for international audiences:

150 km/h sustained winds = 93.2 mph = 81.0 knots

The Saffir-Simpson hurricane scale uses mph: 150 km/h = Category 1 hurricane (sustained 74–95 mph). This translation helps international meteorologists classify cyclones consistently.

Aircraft and maritime

A Boeing 737 cruises at approximately 828 km/h. In knots:

828 ÷ 1.852 = 447 knots

Aviation uses knots universally. Air traffic control, pilot communications, and navigation instruments all speak in knots.

A container ship at 18 knots. In km/h:

18 × 1.852 = 33.3 km/h

Slow compared to land vehicles — but a 400-metre container ship covering 33 km/h carries 10,000+ containers.

Car acceleration

A car goes from 0 to 100 km/h in 6.2 seconds. In mph and m/s:

100 km/h = 62.1 mph → 0–62 mph in 6.2s 100 km/h = 27.78 m/s → average acceleration = 27.78 ÷ 6.2 = 4.48 m/s²

Compare to gravity (9.81 m/s²): this car accelerates at about 0.46g — notable but not supercar territory.

Speed of Sound and Light: Reference Points

Speed of sound in air (at 20°C, sea level): 343 m/s = 1,235 km/h = 767 mph

An aircraft going "Mach 1" travels at this speed. Mach 2 = 2,470 km/h. Concorde cruised at Mach 2.04.

The "crack" of a cricket ball or bullet arises because they travel faster than sound through air.

Speed of light: 299,792,458 m/s ≈ 1,079,252,849 km/h ≈ 670,616,629 mph

Light travels roughly 300,000 km every second — from Earth to the Moon (384,400 km) in about 1.3 seconds.

Speed in Bangladesh Traffic

For daily commuters in Dhaka:

• Legal urban speed limit: 20–30 km/h in some zones, 50 km/h on major roads
• Typical Dhaka city average speed during rush hour: 7–12 km/h
• Expressway speed limit: 100 km/h

Converting for context:

• 12 km/h = 7.5 mph = 3.3 m/s — a brisk walking pace
• 100 km/h = 62 mph = 27.8 m/s

Frequently Asked Questions

What's the difference between speed and velocity? Speed is the magnitude of motion (how fast). Velocity includes direction (how fast, and which way). A car doing 60 km/h northbound has a different velocity from one doing 60 km/h southbound — same speed. Physics equations often require velocity (a vector); everyday usage typically means speed (a scalar).

Why do ships and aircraft use knots? The knot is tied to the nautical mile, which corresponds to one arcminute of latitude. This makes navigation calculations simpler — distance and direction math aligns with geographic coordinates. The convention predates GPS and has persisted through inertia and international standardisation.

Is the speed converter free? Yes — completely free, no sign-up required.

Speed conversions come up in driving, sports, weather, travel, and engineering. The converter handles them all in one place, instantly.

Try the Speed Converter free at sadiqbd.com — convert between km/h, mph, m/s, knots, and more instantly.