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GeekFormat

Unit Converter

1Meter = 100Centimeter
100

International System (SI)

Picometer (pm)1.00×10¹²
Nanometer (nm)1.00×10⁹
Micrometer (μm)1000000
Millimeter (mm)1000
Centimeter (cm)100
Decimeter (dm)10
Meter (m)1
Kilometer (km)0.001
Astronomical Unit (AU)6.68×10⁻¹²
Light Year (ly)1.06×10⁻¹⁶

Imperial

Mil (mil)39370.07874
Inch (in)39.370079
Foot (ft)3.28084
Yard (yd)1.093613
Mile (mi)0.000621
Nautical Mile (nmi)0.00054
Fathom (fm)0.546807
Furlong (fur)0.004971

Chinese Market

Li0.002
Zhang0.3
Chi3
Cun30
Fen300
Hao3000

Free online unit converter and navigation hub offering 36 specialized unit conversion tools covering length, weight, temperature, area, volume, speed, power, pressure, engineering, electrical, medical, and more. Use this page for quick common-unit conversions, or click a category card to enter a dedicated tool page for more comprehensive features, quick-reference tables, and reference materials. Full coverage of Metric, Imperial, and Chinese traditional units. No registration required — all calculations run locally in your browser for privacy.

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About Unit Conversion

Unit conversion is the process of numerically transforming a measurement of the same physical quantity between different units of measurement. Due to historical, regional, and industry differences, multiple unit systems exist worldwide, primarily including the International System of Units (SI, also called Metric), Imperial/US Customary units, and various national traditional units. In international trade, engineering, academic research, and daily life, unit conversion is an essential foundational skill.

The International System of Units (SI) uses the meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd) as its 7 base units, with decimal prefix conversions (kilo, mega, milli, micro, etc.). It is the official standard in the vast majority of countries worldwide and the universal language of science, engineering, and trade.

Imperial units have a long history and are primarily used in the United States, United Kingdom, and former colonies, including the foot, inch, mile, pound, ounce, Fahrenheit, gallon, and psi. Note that some Imperial and US Customary units share the same name but differ in size (e.g., Imperial gallon ≈ 4.546L, US gallon ≈ 3.785L — a difference of about 20%).

Chinese traditional units (shìzhì) include li, zhang, chi, cun, jin, liang, qian, mu, and sheng, now legally defined with fixed Metric conversions (1 jin = 0.5kg, 1 mu ≈ 666.67m²) and still widely used in wet markets, real estate, and daily life. Additionally, the "tsubo" (坪, ≈3.3058m²) commonly used in Japan and Taiwan, the "knot" (1 knot = 1.852km/h) for nautical and aviation use, and the "troy ounce" specific to precious metals are important industry-specific units in certain contexts.

Unit conversion is not just numerical multiplication and division: temperature conversion involves scale offsets (non-linear), data storage has two standards — decimal (hard drive manufacturers) and binary (operating systems), engineering calculations require attention to significant figures and error accumulation, and some industry units (such as shoe sizes and clothing sizes) are not strictly linear conversions and require reference to specific standard tables. GeekFormat provides 36 specialized unit conversion tools; in addition to the general quick converter, each category has an independent dedicated page offering more complete unit coverage, quick-reference tables, and professional reference materials.

Use Cases

  • Cross-border online shopping: quickly convert inches, pounds, Fahrenheit, and US gallons to centimeters, kilograms, Celsius, and liters to compare product dimensions and weights
  • Engineering professionals: convert pressure (psi/MPa/bar), power (kW/HP/PS), torque (N·m/lb·ft), energy (J/cal/BTU) and other units in daily work
  • Home renovation and real estate: convert square feet, tsubo, and acres to square meters, mu, and hectares for floor area calculations; convert inches to centimeters when shopping for building materials
  • Cooking and baking: convert ounces, cups, tablespoons, teaspoons, and US/Imperial gallons to grams and milliliters when adapting international recipes
  • Students: solve length, weight, temperature, speed, force, energy, current, and voltage unit conversion problems in physics, chemistry, and engineering homework
  • Running and fitness: convert pace from min/mi to min/km, weight from pounds to kg/jin, and treadmill speeds between mph and km/h
  • Car maintenance: convert tire pressure between psi/kPa/bar; convert torque units between N·m and lb·ft when servicing imported vehicles
  • International travel: convert Fahrenheit temperatures, mile distances, mph speed limits, mpg fuel economy, and baggage weight limits
  • Foreign trade and cross-border e-commerce: convert product dimensions and weights from Imperial/US to Metric, calculate volumetric weight and shipping costs
  • Appliance shopping: convert BTU/h to watts/kilowatts/"tons" for air conditioners, oven temperatures from °F to °C, and air conditioning cooling capacity units
  • DIY projects, 3D printing, and model building: precise conversion between millimeters, inches, si (丝), and mil (thousandth of an inch)
  • Agriculture and land transactions: quick conversion between mu, hectares, square meters, and acres; convert seed/fertilizer application rates from lb/acre to kg/ha
  • Weather analysis: convert atmospheric pressure between hPa, mmHg, inHg, and mbar
  • Electronics hobbyists: convert AWG wire gauge to mm² cross-sectional area; convert resistance across Ω/kΩ/MΩ, capacitance across pF/nF/μF, and frequency across Hz/kHz/MHz
  • Healthcare scenarios: convert blood glucose between mg/dL and mmol/L; calculate medication dosages by mg/lb body weight; convert body temperature between °F and °C
  • Precious metals investing: convert between troy ounces, grams, liang, and qian; distinguish troy ounces from avoirdupois ounces to avoid measurement errors
  • When unsure which converter you need, navigate from this hub to the corresponding category and enter the dedicated tool page for a more precise conversion experience
  • Academic research and paper writing: look up unit conversion relationships and Metric-Imperial comparison tables to ensure consistent and standardized unit usage in papers

How to Use

  1. In the general quick-convert area on this page, select a unit category, enter a value, choose the source unit and target unit to instantly get the conversion result
  2. For specialized conversion of a specific unit category, browse the category navigation cards above and click the corresponding category (such as length, pressure, temperature, power, etc.) to enter the dedicated tool page
  3. The dedicated tool page provides the complete unit list for that category, batch conversion results, commonly used quick-reference tables, terminology explanations, and in-depth reference content
  4. Click the copy button next to any result to copy the conversion value instantly, convenient for pasting into documents, chats, and spreadsheets
  5. Below the converter you'll find common conversion lookup tables, Metric-Imperial comparison tables, terminology explanations, and best practice guides for ready reference

Features

  • One-stop navigation hub for 36 specialized converter categories: length, mass, temperature, area, volume, speed, time, power, pressure, energy, data storage, angle, force, capacitance, resistance, inductance, frequency, torque, density, viscosity, hardness, illuminance, current, voltage, charge, conductivity, flow rate, magnetic field, radiation, typography, blood glucose, data transfer rate, currency, wire gauge, and more
  • Dual-mode conversion experience: this page provides a general quick converter for everyday needs; click a category card to enter the dedicated tool page for that category's complete unit set, specialized quick-reference tables, and in-depth references
  • Full coverage of three major unit systems: International System of Units (SI/Metric), Imperial/US Customary units, and Chinese traditional units (li, zhang, chi, cun, jin, liang, mu, sheng) — all convertible in one place
  • Precise non-linear temperature conversion: supports accurate offset-aware conversion between Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), and Réaumur (°Ré), with automatic distinction between temperature differences and absolute temperature values
  • Real-time instant results: enter a value to see conversion results immediately, with multiple units in the same category displayed simultaneously — no need to switch target units each time
  • Engineering and professional unit support: includes MPa/psi/bar, kW/horsepower, N·m/ft·lb, Joules/Calories/BTU, AWG wire gauge, mmol/L/mg/dL blood glucose units, and other professional scenario units
  • Pure client-side browser calculation: all conversions run in the frontend with no data uploaded to any server, no plugins to install, protecting your data privacy and security
  • Built-in quick-reference tables and knowledge: includes common conversion lookup tables, unit terminology explanations, Metric vs Imperial comparisons, and best practice guides as in-depth content

Quick Convert vs Dedicated Converters: How to Choose

For occasional everyday conversions, this page is all you need; if you frequently convert a specific category of units (such as engineering pressure, electrical units, blood glucose, flow rate, wire gauge, etc.), we recommend clicking the corresponding category card above to enter the dedicated tool page for a more comprehensive and professional experience.

ComparisonQuick Convert (This Page)Dedicated Category Tools
Best forEveryday quick estimates, ad-hoc conversion needsProfessional work, deep usage, reference material lookup
Unit coverageCommon core unitsComplete unit set for the category (including niche and professional units)
Quick-reference tablesGeneral high-frequency lookup tablesMultiple detailed quick-reference tables specific to the category
Professional contentBasic terminology explanationsIndustry knowledge, best practices, in-depth FAQ
SEO long-tail coverageBroad term «unit converter»Specific long-tail terms (e.g., psi to bar, mmol/L to mg/dL)
Recommended whenOccasional use, quick number lookupsFrequent use of a specific unit category, professional references needed

Best Practices

Do all engineering calculations in SI Metric, convert to Imperial only at the end

When performing engineering, physics, or scientific calculations, use the International System of Units (m/kg/s/Pa/W/°C/K) throughout, then convert final results to Imperial/Chinese units only for display. This avoids accumulated error from multiple conversions and conforms to international academic standards.

Don't apply offsets when converting temperature differences

For temperature differences (e.g., "a temperature change of 10°C" corresponds to "a change of 18°F"), only multiply by the coefficient 9/5 or 5/9 — do NOT add or subtract 32; only specific temperature values (e.g., "air temperature 25°C=77°F") require the offset.

Distinguish US vs Imperial gallons and fluid ounces

US gallon ≈ 3.785L, Imperial gallon ≈ 4.546L — about 20% difference; US fluid ounce ≈ 29.57mL, Imperial fluid ounce ≈ 28.41mL. Always verify when following American/British recipes or refueling across borders, or baking recipes will fail and fuel estimates will be wrong.

Hard drive capacity discrepancy is a unit standard issue, not a defect

Manufacturers label 1TB = 10¹² bytes (decimal), while operating systems calculate in binary at 2⁴⁰ bytes, displaying ≈931GiB — this is normal. Slightly less after formatting and partition table overhead is also normal, so there is no cause for concern.

Consult your vehicle manual for tire pressure, torque, and other safety parameters

Recommended tire pressure and bolt torque vary by vehicle model, tire specification, and load conditions. Unit conversion only solves the numerical transformation — always use the manufacturer's specifications from the B-pillar door jamb sticker or official service manual.

Use troy ounces for precious metals, avoirdupois ounces for everyday items

The "per-ounce price" when buying gold or silver defaults to troy ounces (≈31.1g); food, packages, body weight, and other everyday scenarios use avoirdupois ounces (≈28.35g). Mixing them causes approximately 9.7% measurement deviation.

Use dedicated category tools for professional scenarios

If you need comprehensive conversion for a specific category (such as electrical units, engineering pressure, medical blood glucose, flow rate, wire gauge, etc.), we recommend clicking through from this page to the corresponding dedicated tool page for a more complete unit list, specialized quick-reference tables, and professional reference materials. The general converter is only suitable for quick estimates.

Retain sufficient significant figures before rounding

Keep 4~6 significant figures during intermediate engineering calculation steps, then round final results to 2~3 digits as needed; for daily quick estimates you can use approximate mental math factors directly (e.g., 1in ≈ 2.5cm, 1lb ≈ 0.45kg, 1gal ≈ 3.8L).

FAQ

Is this unit converter free to use? Do I need to register?

Completely free, no registration or login required — just open it in your browser and start converting. All conversions run locally in your browser with no data uploaded, protecting your privacy.

How many centimeters are in an inch? How many meters in a foot?

1 inch (in) = 2.54 centimeters (cm), the exact value defined by the 1959 International Yard and Pound Agreement. 1 foot (ft) = 12 inches = 30.48 cm = 0.3048 meters (m).

How many jin are in a pound? How many pounds in a kilogram?

1 pound (lb, avoirdupois) ≈ 0.4536 kilograms (kg) ≈ 0.9072 jin; 1 kg ≈ 2.2046 lb; 1 jin (Chinese market catty) = 0.5 kg = 500 g ≈ 1.1023 lb. Precious metals use troy pounds: 1 troy pound ≈ 0.3732 kg.

How do you convert Celsius to Fahrenheit? What is the formula?

°C to °F: °F = °C × 9/5 + 32; °F to °C: °C = (°F − 32) × 5/9. Common references: 0°C=32°F (freezing), 20°C=68°F (room temp), 37°C=98.6°F (body temp), 100°C=212°F (boiling); -40°C=-40°F is where both scales coincide.

Why does a 1TB hard drive show only about 931GB on my computer?

Hard drive manufacturers label capacity in decimal (1TB=1000GB=10¹² bytes), while operating systems calculate in binary (1TiB=1024GiB=2⁴⁰ bytes≈1.10TB). So a 1TB drive actually shows ≈931GiB — this is a unit standard difference, not a quality issue. Use our data storage converter to switch between decimal and binary modes.

How do you convert psi, bar, and MPa? What is 2.5 bar tire pressure in psi?

1 psi (pounds per square inch) ≈ 0.06895 bar ≈ 6.895 kPa ≈ 0.006895 MPa; 1 bar = 100 kPa ≈ 14.504 psi ≈ 0.987 atm. Standard passenger car tire pressure of 2.5 bar ≈ 36.3 psi. In engineering, 1 MPa ≈ 145 psi ≈ 10 bar.

How do you convert kilowatts (kW) to horsepower? How many watts is 1 horsepower?

1 kilowatt (kW) ≈ 1.341 mechanical horsepower (HP) ≈ 1.36 metric horsepower (PS); 1 HP ≈ 745.7 W, 1 PS ≈ 735.5 W. US/European cars commonly use HP, German cars use PS; the two differ by only about 1.4%.

Are US gallons and Imperial gallons the same? How many gallons are in a liter?

No, they differ by about 20%. 1 liter (L) ≈ 0.2642 US gallons (US gal ≈3.785L) ≈ 0.2200 Imperial gallons (UK gal ≈4.546L). American recipes use US units, Commonwealth countries use Imperial — do not mix them.

There are 36 converter tools here — how do I choose which one to use?

If you just need a quick estimate for a common unit, use the general quick converter on this page. If you need specialized conversion for a specific category (such as engineering pressure, electrical units, blood glucose, flow rate, wire gauge, etc.), click the corresponding category card to enter the dedicated tool page, where you'll find a more complete unit list, quick-reference tables, and professional reference materials.

Why isn't temperature conversion simple multiplication? Are temperature difference conversions the same as temperature value conversions?

Empirical temperature scales like Celsius and Fahrenheit have different zero points (0°C=32°F), so they have an affine relationship (offset + coefficient), not a proportional one. Temperature differences (e.g., "a temperature increase of 10°C" corresponds to "an increase of 18°F") only multiply by the coefficient 9/5 without adding or subtracting 32; only absolute temperature values require the offset.

Does it work offline? Can I use it on my phone?

Yes — once the page loads, it works normally even without an internet connection. The page is fully responsive, so you can use it directly in your browser on phones, tablets, and computers with no app download needed.

How many square meters are in a mu? How many mu are in a hectare?

1 mu (Chinese acre) ≈ 666.67 square meters (exactly 2000/3 m²). 1 hectare (ha) = 10,000 square meters = 15 mu; 1 square kilometer = 100 hectares = 1,500 mu; 1 acre ≈ 4046.86 square meters ≈ 6.07 mu.

Glossary

International System of Units (SI)
Also known as the Metric system, with 7 base units: meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd). It is the officially used unit system in the vast majority of countries worldwide, using decimal conversions, and is the universal standard in science and engineering.
Imperial / US Customary Units
Historical unit systems used in the UK, US, and other countries, including feet, pounds, Fahrenheit, gallons, miles, and psi. Note that some units share names but differ in size between Imperial and US Customary (Imperial gallon ≈ 4.546L, US gallon ≈ 3.785L) — do not mix them.
Chinese Traditional Units (Shìzhì)
Traditional Chinese measurement units including li, zhang, chi, cun, jin, liang, qian, mu, and sheng. Legally defined with fixed Metric conversions (1 jin = 0.5kg, 1 mu ≈ 666.67m²), still widely used in wet markets, real estate, and rural daily life.
Absolute Temperature Scale
Temperature scales with zero point at absolute zero (the theoretical temperature where molecular thermal motion ceases), including Kelvin (K) and Rankine (°R). K = °C + 273.15; °R = °F + 459.67. Scientific calculations and thermodynamics formulas require absolute temperature scales.
SI Prefix (Decimal)
Prefixes in the International System of Units used to scale base units up or down, such as k (kilo, 10³), M (mega, 10⁶), G (giga, 10⁹), m (milli, 10⁻³), μ (micro, 10⁻⁶), n (nano, 10⁻⁹), etc. Each prefix differs by a factor of 1000, commonly used in daily engineering calculations.
IEC Prefix (Binary)
Used exclusively for computer storage capacity: Ki (kibi, 2¹⁰≈10³), Mi (mebi, 2²⁰≈10⁶), Gi (gibi, 2³⁰≈10⁹), Ti (tebi, 2⁴⁰≈10¹²), corresponding to KiB/MiB/GiB/TiB. These differ from decimal KB/MB/GB/TB by about 2.4%~10%, which is the root cause of hard drive capacity discrepancies.
psi
Pounds per Square Inch, an Imperial pressure unit widely used for tire pressure, hydraulics, pneumatics engineering, and the oil/gas industry. 1 psi ≈ 6.895 kPa ≈ 0.06895 bar ≈ 0.006895 MPa.
Horsepower (HP/PS)
Power units. Mechanical/Imperial horsepower (HP/hp) = 550 ft·lb/s ≈ 745.7W; metric horsepower (PS) = 75 kgf·m/s ≈ 735.5W. The two differ by about 1.4%. In everyday Chinese usage, "horsepower" usually refers to metric horsepower.
Troy Ounce (oz t)
A weight unit used exclusively for precious metals (gold, silver, platinum). 1 troy ounce ≈ 31.1035 grams, about 9.7% heavier than an avoirdupois ounce (≈28.35g). 1 troy pound = 12 troy ounces (unlike the avoirdupois pound of 16 ounces) — take special care to distinguish when investing in precious metals.
Tsubo (坪)
An area unit originating from Japan, also widely used in Taiwan and Korea. 1 tsubo = 2 tatami mats ≈ 3.3058 m² ≈ 35.58 sq ft, commonly seen in Hong Kong/Taiwan real estate listings and Japanese rental area calculations.

Most Common Conversions Quick Reference

ConversionEquivalent
1 inch (in)= 2.54 cm
1 foot (ft)= 30.48 cm = 0.3048 m
1 mile (mi)≈ 1.609 km
1 pound (lb)≈ 0.4536 kg ≈ 0.907 jin
1 ounce (oz, avoirdupois)≈ 28.35 g
0°C= 32°F
100°C= 212°F
1 m²≈ 10.76 sq ft
1 mu≈ 666.67 m²
1 hectare (ha)= 15 mu = 10,000 m²
1 US gallon (US gal)≈ 3.785 L
1 Imperial gallon (UK gal)≈ 4.546 L
1 bar≈ 14.5 psi ≈ 100 kPa
1 kilowatt (kW)≈ 1.34 HP ≈ 1.36 PS
1 knot= 1.852 km/h ≈ 1.15 mph

SI (Metric) Decimal Prefix Table

PrefixSymbolFactorExample
nanon10⁻⁹nm (nanometer), ns (nanosecond)
microμ10⁻⁶μm (micrometer), μs (microsecond), μF (microfarad)
millim10⁻³mm (millimeter), mg (milligram), ms (millisecond)
centic10⁻²cm (centimeter)
kilok10³km (kilometer), kg (kilogram), kW (kilowatt)
megaM10⁶MB (megabyte), MPa (megapascal), MHz (megahertz)
gigaG10⁹GB (gigabyte), GHz (gigahertz), GPa (gigapascal)
teraT10¹²TB (terabyte), THz (terahertz)