Unit conversion basics: length, weight, and temperature

Unit conversion means rewriting the same quantity in another unit. For length and weight you multiply or divide by a fixed factor. For temperature you use a formula, not a single multiplier. The unit converter applies those rules in the browser. Three checks from the same library: 100 cm is 39.3701 in, 70 kg is 154.3236 lb, and 20 °C is 68 °F (four decimal places where needed).

The method in one sentence

Pick a category, enter a value, choose the from and to units, and read the live result plus the formula line. Length and weight go through a shared base (metre or kilogram). Temperature goes through kelvin so Celsius, Fahrenheit, and Kelvin stay consistent with each other.

Length: centimetres, inches, feet

The international inch is defined as exactly 0.0254 m, so one centimetre is 0.01 m. To go from centimetres to inches:

inches = centimetres × (0.01 / 0.0254)

Worked example: 100 cm to inches

Enter 100 under length, from cm to in. The result is 39.37007874015748 raw, or 39.3701 at four decimal places. That is the familiar “about 39.37 inches in a metre of tape,” written for a 100 cm stick.

Worked example: 175 cm as feet and inches

Many clothing and height forms want feet plus leftover inches, not a single decimal foot. 175 cm is 1.75 m. Splitting that into feet and inches gives 5 ft and 8.8976 in (inches rounded to four places). In the tool, use the length preset for centimetres to feet and inches, or convert to feet (5.7415 ft at four places) and read the compound line when the UI shows it.

A one-metre rod is 3.2808 ft at four decimal places. Five kilometres is 3.1069 mi. Same length category, same factor table.

Weight: kilograms and pounds

The avoirdupois pound is defined as exactly 0.45359237 kg. To convert kilograms to pounds:

pounds = kilograms / 0.45359237

Worked example: 70 kg to pounds

70 ÷ 0.45359237 ≈ 154.3235835294143. At four decimal places the display is 154.3236 lb. Swap units and enter that pound value to return close to 70 kg (tiny gaps come only from display rounding).

Worked example: 250 g to ounces

250 g converts to about 8.8185 oz at four decimal places. Use this for grocery labels or packing lists when the package shows grams and you think in ounces.

Temperature: Celsius to Fahrenheit

Temperature is not a straight multiply. Degrees Celsius and Fahrenheit share a shifted, scaled relationship. A short path through the converter:

°F = (°C × 9/5) + 32

Worked example: 20 °C to Fahrenheit

(20 × 9/5) + 32 = 68. The tool returns 68 exactly for that pair. The reverse (68 °F to Celsius) returns 20. Room-temperature labels and weather apps use this pair constantly.

For freezing and boiling of water under common lab teaching numbers, 0 °C maps to 273.15 K and 100 °C maps to 373.15 K. The companion article on Celsius, Fahrenheit, and Kelvin walks those formulas in more detail.

How to use the unit converter

1. Open the unit converter.
2. Choose the Length, Weight, or Temperature tab.
3. Set the from and to units, then type the value.
4. Adjust precision if you need fewer or more decimal places.
5. Use Swap to reverse the units, Copy for the result, or Reset to clear the fields.

Common conversion chips (cm to feet and inches, kg to pounds, Celsius to Fahrenheit) load sample values immediately. Nothing is sent to a server.

Common mistakes

Mixing factors across categories. An inch factor does not convert grams. Confirm the tab matches the quantity.

Treating temperature like length. Multiplying Celsius by 1.8 without adding 32 is incomplete. Use the full formula or the temperature tab.

Rounding too early. If you round 70 kg to “about 154 lb” and convert back, you will not recover 70. Keep precision mid-chain; round once at the end.

Confusing decimal feet with feet-and-inches. 5.7415 ft is not “5 feet and 7415 inches.” Clothing charts usually want leftover inches after whole feet.

Assuming every regional land unit is universal. Units such as marla or bigha can vary by place. This site omits unverified regional area units rather than inventing factors.

When length and weight show up together

Height in centimetres and weight in kilograms often share one form. Convert each on its own tab. If you later need a body-mass index, convert first, then use the BMI calculator. BMI is a separate formula, not a unit swap.

Try the three checks

Confirm 100 cm to 39.3701 in, 70 kg to 154.3236 lb, and 20 °C to 68 °F with precision set to four decimals (temperature may show fewer trailing zeros). Then try 175 cm with the feet-and-inches preset.