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To convert mph to km/h, multiply by 1.60934. So 60 mph = 96.56 km/h, 70 mph = 112.65 km/h, and 100 mph = 160.93 km/h. A useful mental shortcut: add 60% to the mph value for an approximate km/h equivalent. 50 mph + 50% = 75 km/h (actual: 80.47 km/h) — close enough for casual estimation.
Most countries set highway speed limits in km/h: France 130, Germany (Autobahn, unrestricted sections), and Japan 100 km/h. The US and UK use mph: US interstates typically 65–75 mph (105–120 km/h), UK motorways 70 mph (113 km/h). Understanding both is essential when driving internationally or comparing car performance specs from different markets.
Did you know? Only five countries use mph as their primary road speed unit: the US, UK, Myanmar, Liberia, and the British territories of Antigua and Barbuda. Every other nation uses km/h, making mph-to-kph one of the most practically useful speed conversions for travelers.
Renting a car in Europe as an American driver: road signs show km/h, but your mental speed reference is in mph. Comparing car specs — European manufacturers advertise 0–100 km/h, US manufacturers advertise 0–60 mph (the same test, different units). GPS apps switching between region presets need this conversion for speed alerts.