KM to Miles Converter (All Length Units)

Kilometers to Miles – Exact Relation 1 mi = 1.609344 km

Core idea: The mile is legally defined as exactly 1609.344 meters. 1 km = 1000 m, so 1 km / 1609.344 m = 0.6213711922… mi.

Formulas

• mi = km ÷ 1.609344
• Simplified: mi = km × 0.6213711922 (keep ≥10 significant digits for precision work)
• Inverse: km = mi × 1.609344
• Speed interplay: mph = (km/h) × 0.6213711922

Quick Values

Worked Example

Convert 18.4 km to miles: 18.4 ÷ 1.609344 = 11.430115 mi. Rounded to 4 decimals → 11.4301 mi. Reverse: 11.430115 × 1.609344 ≈ 18.4 km.

Where Used

• Travel & navigation (metric route planning vs imperial signage).
• Running / cycling event distance comparisons (5K, marathon).
• Automotive instrumentation (km/h ↔ mph conversions).

Accuracy & Tips

• Use full factor 1.609344 for conversions—avoid 1.61 (adds ~0.03% error).
• For quick head math: km × 0.62 (underestimates slightly) or × 5/8 ( = 0.625, close).
• Report to context: travel (2–3 dp), scientific (≥6 dp).

More Examples

FAQ

• How many miles in 1 km? 0.6213711922 miles.
• How many km in 1 mile? 1.609344 km (exact).
• Most common rounding? 0.621 or 0.62—state which you use.

Miles definition fixed by treaty; factor exact.