Conversion Calculator

One place for everyday unit conversions

This page keeps common unit types in one simple tool. Use the tabs for length, area, angle, speed, temperature, time, volume, weight and pressure. Instead of juggling multiple conversion charts, mental math and separate apps, you pick a category, choose “from” and “to” units, enter a value, and see a clean line like “20 ft = 6.096 m”.

1. Choose the right tab

Start by selecting the category that matches what you are working with. This general conversion calculator is tuned for practical, real-world measurements:

• Length for inches, feet, yards, miles and metric lengths down to micrometres and nanometres.
• Area for square feet, square yards, acres, square metres, hectares, ares and square miles.
• Angle for radians, milliradians, degrees, arcminutes, arcseconds, gradians, revolutions/circles and mils.
• Speed for knots, mph, ft/s, km/h, m/s, km/s, cm/s and reference speeds like Mach 1 and the speed of light.
• Temperature to switch between °F, °C, K, Rankine, Delisle and Newton scales.
• Time for centuries, decades, years, months, weeks, days, hours, minutes, seconds and down to microseconds and nanoseconds.
• Volume for US teaspoons, tablespoons, cups, fluid ounces, pints, quarts, gallons and metric litres, mL, cm³ and m³.
• Weight for ounces, pounds, stones, short tons, long tons, metric tons and metric grams from kg down to mg and carats.
• Pressure for psi, bar, Pascal, atmosphere, millibar, hectopascal, kilogram-force per area, pounds per square foot and Torr.

When you switch tabs, the “Convert from” and “Convert to” lists update so you only see units that belong to that measurement family, with US-style units listed first where it makes sense. That keeps the interface compact while still behaving like a full-featured unit converter.

2. The base-unit method behind the scenes

For most categories, the conversion is a base-unit method. The tool first converts your entry into a core SI unit, then into the target unit. In symbols:

value_base = value_from × factor_from→base
value_to = value_base ÷ factor_to→base

Examples:

• Length: everything is routed through metres (m). Inches, feet, miles, micrometres and nanometres are all turned into metres, then back out into your chosen unit.
• Area: everything goes through square metres (m²). That keeps acres, ares, square feet and hectares consistent with metric land areas.
• Time: everything is based on seconds. Centuries, decades, years, weeks and days are multiples of seconds; milliseconds, microseconds and nanoseconds are tiny fractions.
• Weight: everything passes through kilograms (kg) so pounds, ounces, stones, short tons, long tons, metric tons and carats line up cleanly.
• Volume: everything runs through cubic metres (m³), tying US gallons and cups to litres, millilitres and cubic centimetres.
• Pressure: everything flows through Pascals (Pa), so psi, bar, atm, hPa, mbar, kgf/cm², kgf/m², psf and Torr all stay consistent with each other.

3. Temperature: offset plus scale

Temperature is different because the zero points and step sizes don’t match. That is why the tool uses formulas instead of just one factor:

°C = (°F − 32) × 5 / 9
K = °C + 273.15
°C = 100 − (°De × 2 / 3)
°C = °N × 100 / 33

Converting °F to °C removes the 32-degree offset and rescales the result. Kelvin and Rankine are then just constant offsets and scale changes around the same temperature ladder, so this online temperature converter can move smoothly between all six scales.

4. Reading and reusing the result

The result box always shows a single clean line like “5 lb = 2.268 kg”. Values are rounded to a sensible number of digits: enough precision for everyday work, home projects, school assignments and quick engineering estimates, but not so many that the numbers become unreadable. If you’re running several calculations in a row, use this as a check and keep a few extra digits on your own sheet, rounding only at the end.

Conversion factors at a glance

If you just need a rough factor to do mental math or check a result from the converter, this compact table shows how starting units, resulting units and factors line up for some of the most common measurements.

Common conversions you’ll see all the time

Here are some of the most common “back-of-the-envelope” conversions, written out the same way you might jot them on a notepad while using this measurement converter:

Area conversions

• 1 sq mi = 640 acres ≈ 2.59 sq km
• 1 acre = 43,560 sq ft ≈ 4,047 sq m
• 1 sq ft ≈ 0.093 sq m
• 1 sq km = 1,000,000 sq m ≈ 247.1 acres

Length conversions

• 1 mi = 5,280 ft ≈ 1.609 km
• 1 ft = 12 in ≈ 0.305 m ≈ 30.48 cm
• 1 in = 2.54 cm = 25.4 mm
• 1 km = 1,000 m ≈ 0.621 mi
• 1 m ≈ 39.37 in ≈ 3.281 ft
• 1 cm = 10 mm ≈ 0.394 in
• 1 mm ≈ 0.0394 in

Volume conversions

• 1 U.S. gallon = 4 quarts = 8 pints ≈ 3.785 liters
• 1 liter ≈ 2.113 pints ≈ 1.057 quarts ≈ 0.264 U.S. gallons

Weight / mass conversions

• 1 ton (short) = 2,000 lb ≈ 907.1847 kg
• 1 lb = 16 oz ≈ 453.592 g
• 1 oz ≈ 28.3495 g
• 1 kg = 1,000 g = 1,000,000 mg ≈ 2.20462 lb

The calculator applies the same ideas automatically and keeps extra precision in the background, so you can type what you have, pick what you need, and read the result without memorising every factor or pulling out a separate conversion table.

References and further reading on unit conversions

The conversion factors in tools like this are based on standard SI guidance and tables from national and international metrology bodies. For deeper detail or exact factors, these resources are a good starting point:

• NIST Guide to the SI — Appendix B: Conversion Factors — provides vetted conversion factors between U.S. customary units and SI units across many quantities including length, area, volume, mass, pressure and more.
• NIST Metric Program — Unit Conversion overview — explains how to use conversion factors, rounding and significant digits when moving between metric and U.S. customary units.
• Bureau International des Poids et Mesures — SI Brochure — the core reference for the International System of Units (SI), including definitions of base and derived units and guidance on consistent measurement.

For critical engineering, lab or safety work, always compare tool results against official tables or your organisation’s standards and keep enough significant digits for your calculations.