Fixed factors
Metric prefixes and many SI-related conversions use defined factors, so these are suitable for everyday arithmetic checks. Rounding still affects the displayed answer.
Unit Converter
Clear Calculators everyday converter
Convert metric, imperial and everyday units.
Length
Everyday metric and imperial distance units.
Rounding
About length
DistanceLength conversions use metres as the base unit, then translate between metric and imperial distances.
For height, choose Feet + inches to enter values the way people usually say them.
Everyday examples
PracticalRecent results
Unit converter for everyday measurements
Convert metric and imperial units for length, weight, volume, temperature, area, speed, pace, time, data, data rate, energy, cooking, pressure, power, electricity, voltage, resistance, capacitance, inductance, conductance, magnetism, charge, light, sound, radiation, radioactivity, concentration, viscosity, flow rate, paper sizes, clothing sizes and shoe sizes. Treat practical comparisons as estimate-only guidance where brand charts, recipes or specifications differ.
Use it for common searches like mph to km/h, min/km to km/h, kg to lb, cm to inches, litres to pints, Celsius to Fahrenheit, Mbit/s to MB/s, dB SPL to pascals, gauss to tesla, cP to mPa s, curies to becquerels, A4 to US Letter, UK to EU shoe sizes and UK to EU clothing sizes.
How conversions are calculated
Most unit conversions use a base unit behind the scenes. For length, the calculator can convert the starting value into metres and then convert metres into the target unit. For weight, it can use grams or kilograms as a practical base. For speed, it converts through a distance-over-time relationship, which is why miles per hour and kilometres per hour can be compared directly.
Temperature is different because Celsius, Fahrenheit and Kelvin do not share the same zero point. Those conversions use a formula rather than a simple multiplier. The result panel shows a plain-English sentence and the formula area explains the method for the selected category.
When to use approximate conversions
Some categories are exact mathematical conversions, while others are practical approximations. Shoe size and clothing size conversions can vary by brand, fit, width and country. Paper size comparisons can also involve different aspect ratios, so the result is best used for rough planning rather than print production without checking dimensions.
Cooking units can be another source of confusion because a cup, tablespoon or fluid ounce can mean different things in different countries. Choose the closest matching unit in the list and check the recipe source if the measurement is important.
The search box is useful when you know the unit but not the category. Try terms such as mph, kg, A4, PSI, horsepower, cup, tablespoon, shoe size or pixels to jump straight to relevant choices.
Common unit conversion examples
Everyday checks| Search | Approximate result | Useful for |
|---|---|---|
| 60 mph to km/h | 96.56 km/h | Driving, travel and road-speed comparisons. |
| 1 kg to lb | 2.20 lb | Parcels, luggage, food labels and gym weights. |
| 3 metres to feet | 9.84 ft | Room widths, DIY and rough property measurements. |
| 180 cm to feet and inches | About 5 ft 11 in | Height comparisons in a more familiar format. |
| 250 ml to US cups | About 1.06 US cups | Recipes, baking and kitchen conversions. |
Accuracy notes
LimitsApproximate categories
Shoe sizes, clothing sizes, paper comparisons and some cooking measures are practical comparisons. Brand charts, recipes and print specifications can use different assumptions.
Technical use
For engineering, laboratory, medical, legal, safety or manufacturing work, check the relevant standard, tolerance, instrument calibration or professional guidance before relying on a rounded result.
Source notes: SI unit and prefix context checked against BIPM SI information, BIPM SI prefixes and NIST SI units. Last reviewed 13 June 2026.
Common conversion mistakes
Worth checkingUS and UK units
A US gallon, US pint or US cup is not the same as a UK gallon, UK pint or metric cup. Pick the labelled unit that matches the source.
Mass and weight
Everyday searches often say weight for kilograms and pounds. Technical work may need mass, force or local gravity handled separately.
Rounded answers
A rounded result is easier to read, but it can be too rough for small tolerances. Use more decimal places when tiny differences matter.
Unit converter FAQs
Quick answersAre all unit conversions exact?
Many metric, imperial and SI-style conversions use fixed factors, but some everyday comparisons are approximate. Clothing sizes, shoe sizes, cooking cups and paper sizes can vary by country, brand or context.
Why are temperature conversions different?
Temperature scales do not share the same zero point, so Celsius, Fahrenheit and Kelvin conversions use formulas rather than a simple multiplication factor.
What does smart rounding mean?
Smart rounding chooses a practical number of decimal places for the selected unit. You can switch to a fixed number of decimal places when you need a more consistent display.
Can I use this converter for technical work?
The converter is useful for everyday checks and planning. For engineering, laboratory, medical, legal or safety-critical work, check the relevant specification, instrument tolerance or professional standard.
Why do recipe conversions differ between websites?
Recipe units such as cups, tablespoons and fluid ounces can use different national definitions. The converter labels UK, US and metric-style units where the distinction matters.