Unit Converter (in-cm, lb-kg, F-C, mph-km/h)

The Quick Unit Converter is designed for high intent, everyday conversions. Instead of overwhelming you with hundreds of units, it focuses on what people search for most often: inches to centimeters, pounds to kilograms, Fahrenheit to Celsius, and miles per hour to kilometers per hour. That makes the results fast, reliable, and easy to read.

The tool is organized into four groups:

• Length: inches and centimeters, feet and meters, miles and kilometers
• Weight: pounds and kilograms, ounces and grams
• Temperature: Fahrenheit, Celsius, and Kelvin
• Speed: miles per hour and kilometers per hour

This is intentionally compact. You can still solve the majority of everyday conversion problems without hunting through long menus.

Rounding may affect results; confirm critical measurements.

Length conversions are some of the most common, especially when you move between US and metric standards. The tool uses exact constants:

• 1 inch = 2.54 cm
• 1 foot = 0.3048 m
• 1 mile = 1.609344 km

Examples:

• 12 in to cm: 12 * 2.54 = 30.48 cm
• 6 ft to m: 6 * 0.3048 = 1.8288 m
• 3 mi to km: 3 * 1.609344 = 4.828032 km

Use the precision selector to round to the level you need. For many everyday tasks, two decimals is enough.

Weight conversions are common in fitness, cooking, and shipping. This tool supports pounds, kilograms, ounces, and grams using exact constants:

• 1 lb = 0.45359237 kg
• 1 oz = 28.349523125 g

Examples:

• 150 lb to kg: 150 * 0.45359237 = 68.0389 kg
• 1 kg to lb: 1 / 0.45359237 = 2.20462 lb
• 16 oz to g: 16 * 28.349523125 = 453.592 g

If you are tracking weight changes, consider rounding to one or two decimals for consistency.

Temperature is a special case because it is not a simple multiplication. Fahrenheit and Celsius use different zero points, so the formulas include offsets:

• C = (F - 32) * 5/9
• F = C * 9/5 + 32
• K = C + 273.15

Examples:

• 32 F to C: (32 - 32) * 5/9 = 0 C
• 68 F to C: (68 - 32) * 5/9 = 20 C
• 100 C to F: (100 * 9/5) + 32 = 212 F
• 25 C to K: 25 + 273.15 = 298.15 K

Because temperature conversions often create decimals, rounding is expected. Use the precision selector to match your reporting needs.

Speed conversions are straightforward, and the tool handles the most common pair: miles per hour and kilometers per hour.

• 1 mph = 1.609344 km/h

Examples:

• 55 mph to km/h: 55 * 1.609344 = 88.51392 km/h
• 100 km/h to mph: 100 / 1.609344 = 62.1371 mph

This is helpful for travel planning, driving abroad, and interpreting international speed limits.

The precision selector lets you choose how many decimals to display. Here is a simple rule of thumb:

• 0 to 1 decimals: quick mental math or rough estimates
• 2 decimals: everyday use, shopping, or reporting
• 3 to 6 decimals: scientific or engineering work

Even when you round the displayed value, the underlying conversion uses the exact constants listed above.

The converter applies fixed conversion ratios between units and formats the result to your chosen precision. It does not round intermediate values unless you set rounding.

Convert 5 miles to kilometers: 5 * 1.60934 = 8.0467 km (rounded to 8.05 km).

Use this tool when you need quick, reliable unit conversions for travel, measurements, or data cleanup. It is useful for everyday reference and cross-unit comparisons.