मुफ़्त इकाई कनवर्टर ऑनलाइन
लंबाई, वज़न, तापमान, डिजिटल संग्रहण, गति, समय और क्षेत्र को तुरंत कनवर्ट करें।
यह कैसे काम करता है
एक श्रेणी चुनें, अपनी "से" और "तक" इकाइयाँ चुनें, फिर किसी एक फ़ील्ड में मान दर्ज करें। रूपांतरण तुरंत होता है।
समर्थित श्रेणियाँ
- लंबाई · मिलीमीटर, सेंटीमीटर, मीटर, किलोमीटर, इंच, फ़ुट, गज़, मील
- भार · मिलीग्राम, ग्राम, किलोग्राम, औंस, पाउंड, टन
- तापमान · सेल्सियस, फ़ारेनहाइट, केल्विन
- डिजिटल संग्रहण · बाइट, KB, MB, GB, TB, PB
- गति · m/s, km/h, mph, नॉट
- समय · सेकंड, मिनट, घंटे, दिन, सप्ताह, महीने, वर्ष
- क्षेत्रफल · वर्ग मीटर, वर्ग फ़ुट, एकड़, हेक्टेयर, वर्ग किमी, वर्ग मील
अक्सर पूछे जाने वाले प्रश्न
रूपांतरण कितने सटीक हैं?
सभी रूपांतरण मानक गणितीय सूत्र और JavaScript फ़्लोटिंग-पॉइंट परिशुद्धता (लगभग 15 अंक) का उपयोग करते हैं।
क्या मैं दोनों दिशाओं में रूपांतरित कर सकता हूँ?
हाँ। किसी भी फ़ील्ड में टाइप करें और दूसरा तुरंत अपडेट होता है। रूपांतरण हमेशा द्विदिशीय और वास्तविक समय में होता है।
क्या मुद्रा रूपांतरण समर्थित है?
फ़िलहाल नहीं। मुद्रा विनिमय दरें लगातार बदलती हैं और API के माध्यम से लाइव डेटा की आवश्यकता होती है। क्योंकि हमारे टूल ऑफ़लाइन चलते हैं, मुद्राएँ समर्थित नहीं हैं।
A short history of measurement
For most of recorded history the units people used were derived from the human body, a body part is always with you, no calibrated tool required. The cost was that no two bodies matched. The Egyptian cubit ran from elbow to fingertip, divided into 7 palms of 4 digits each; the "royal cubit" used for the pyramids has been measured at about 52.3 cm on surviving rods. The Roman pes (foot) was about 29.6 cm, divided into 12 unciae: the etymological root of both "inch" and "ounce." A fathom was the span of outstretched arms, a sailor's natural way of measuring rope; an inch was traditionally the width of an adult thumb at the knuckle, codified by Edward II in 1324 as "three barleycorns laid end to end."
By the late 18th century pre-Revolutionary France was estimated to have at least 250,000 different units in active use because each town, each guild and each commodity had its own. Trade required converting between dozens of mutually incompatible units; disputes were endemic; peasants paid feudal dues measured in local units that landlords could redefine at will. In 1790 the French National Assembly invited the Académie des sciences to design "a system of weights and measures whose model would be drawn from nature." The commission (Lagrange, Laplace, Monge, Condorcet and Lavoisier) proposed a decimal system anchored to two natural references: the metre as one ten-millionth of the distance from the North Pole to the Equator along the Paris meridian, and the kilogram as the mass of a cubic decimetre of water at melting-ice temperature. France formally adopted the metric system on 7 April 1795.
In 1875, after eighty years of slow international adoption and growing concerns that copies of the standards were drifting from the Paris originals, 17 nations including the United States signed the Treaty of the Metre in Paris on 20 May. It established the General Conference on Weights and Measures (CGPM), the International Committee for Weights and Measures (CIPM), and the International Bureau of Weights and Measures (BIPM), all still operating today. The BIPM laboratory is at the Pavillon de Breteuil in Sèvres, just outside Paris, and is technically extraterritorial; French police cannot enter without permission.
SI: the seven base units
The 11th CGPM in 1960 formally established the Système international d'unités (SI). Seven base units, from which every other unit is derived:
| Quantity | Base unit | Symbol |
|---|---|---|
| Length | metre | m |
| Mass | kilogram | kg |
| Time | second | s |
| Electric current | ampere | A |
| Temperature | kelvin | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
A newton is kg·m/s². A joule is N·m. A watt is J/s. The system is intentionally minimal and self-consistent.
On 20 May 2019 (World Metrology Day, the anniversary of the 1875 Treaty), the SI was redefined so that all seven base units are now anchored to fixed numerical values of physical constants, speed of light, Planck's constant, the caesium-133 hyperfine frequency, the Boltzmann constant, the Avogadro constant, the elementary charge, and a defined luminous efficacy. The kilogram was the last hold-out, defined since 1889 as the mass of a particular platinum-iridium cylinder kept under three nested bell jars in a vault in Sèvres. Nicknamed Le Grand K, the cylinder had been losing weight relative to its sister copies at about 50 micrograms per century, small absolutely, but unacceptable for what was supposed to be a perfect constant. After 130 years, Le Grand K was retired and the kilogram is now defined via Planck's constant. The practical effect for an end user typing "1 kg = ? lb" into a converter is exactly nothing (the new kilogram was defined to match the old to within a few parts in 10⁸) but the new kilogram is no longer aging.
The three countries that didn't switch
Only three countries officially still use US customary or imperial units as their primary system: the United States, Liberia and Myanmar. Even the United Kingdom, origin of the imperial system, has been officially metric since 1965, though pints, miles and stones survive in retail and on road signs. The US situation is more nuanced than "Americans don't use metric":
- All US science is metric. NASA, the NIH, the NSF and every research university publish in SI. Curiosity rover specs are in cm and kg.
- US medicine is metric. Prescriptions in milligrams; IV drips in millilitres per hour; the Joint Commission's 2017 paediatric standards push for kg-only weight recording to prevent the 2.2× overdoses that came from confusing pounds and kilograms.
- The US military is metric. Tactical maps, ammunition (5.56 mm, 7.62 mm, 9 mm), joint NATO operations all require it.
- US retail and construction stay imperial, mostly because the 1975 Metric Conversion Act made the switch voluntary rather than mandatory and there has been no political appetite to compel it.
The cost of mixed systems can be high. In 1999 the Mars Climate Orbiter was lost (a $125M mission) because Lockheed Martin's ground software produced thruster impulse data in pound-force seconds while NASA's flight software expected newton-seconds. The orbital insertion burn fired with the wrong magnitude, the spacecraft entered the Martian atmosphere too low, and was destroyed.
Conversions worth knowing exactly
Several common conversions are exact by international agreement (since 1959):
- 1 inch = 2.54 cm: exact, by the 1959 international yard-and-pound agreement.
- 1 mile = 1.609344 km: exact.
- 1 lb = 0.45359237 kg: exact.
- °F = (°C × 9/5) + 32 with the famous −40 = −40 coincidence (the only temperature where the two scales agree).
- K = °C + 273.15 exactly. Absolute zero is −273.15 °C.
The volume gallon trap. US gallon ≈ 3.785 L; UK ("Imperial") gallon ≈ 4.546 L. The two are 20% different despite sharing the word "gallon", the UK redefined its gallon in 1824 and the US kept the older Queen Anne (1707) wine gallon. Recipe substitution between US and UK cookbooks has been a quiet source of cooking disasters for two centuries. (This converter doesn't include volume; consult a dedicated volume calculator and pick the right gallon.)
Temperature scales, three different zeros
Fahrenheit (1724) was Daniel Gabriel Fahrenheit's scale anchored to a brine ice-bath at 0°F and (according to one of his explanations) human body temperature at 96°F, though the body-temperature anchor turned out to be off by about 2.6 degrees. The scale survives in the US and Caribbean.
Celsius (1742) was Anders Celsius's scale, originally inverted: water boiled at 0° and froze at 100°. Carl Linnaeus and others flipped it within two years to today's water-freezes-at-0, water-boils-at-100. Used essentially everywhere except the US.
Kelvin (1848), proposed by William Thomson (Lord Kelvin), is an absolute scale, 0 K is absolute zero, the point at which classical molecular motion stops. The kelvin is the SI unit and is used in physics and chemistry. Note: temperatures in kelvins are written without the degree sign (300 K, not 300 °K).
Mass vs weight, they're not the same thing
The pedant's distinction. Mass (measured in kilograms) is a property of an object, how much "stuff" it contains, measured by its inertia. Weight (measured in newtons in proper SI) is the force that mass experiences in a gravitational field: W = m × g, where g ≈ 9.81 m/s² on Earth. A 70 kg person masses 70 kg whether they're on Earth, the Moon, or in orbit, but weighs roughly 686 N on Earth, 113 N on the Moon, and effectively zero in free fall.
In everyday speech (and on this converter) we treat the two interchangeably and use kilograms or pounds for both, which is fine on Earth's surface where g is roughly constant, but wrong in physics class and in any space-related context. The pound is also overloaded: the "pound" you weigh in is technically the pound-mass (lbm), distinct from the pound-force (lbf) used in engineering, and their numerical equality on Earth is a coincidence of the gravitational acceleration value, not a conversion factor.
More questions
Why is a US gallon different from a UK gallon?
Because the UK redefined its gallon in 1824 (the Imperial gallon, defined as the volume of 10 lb of water at 62°F, ≈ 4.546 L) while the US kept the older Queen Anne wine gallon of 1707 (≈ 3.785 L). The two are about 20% different. Same word, different volumes, a recurring trap in international cooking, brewing and shipping calculations. Always check which "gallon" a recipe or specification means.
Why does 1 KB sometimes mean 1024 bytes and sometimes 1000?
Because two competing conventions coexist. SI prefixes are decimal: 1 kilobyte = 1000 bytes, 1 megabyte = 1,000,000 bytes. This is what hard-drive manufacturers, network speeds and file-size displays in macOS use. The binary prefixes (kibibyte KiB = 1024 B, mebibyte MiB = 1024² B) were introduced by IEC in 1998 to disambiguate, but Microsoft Windows still labels 1024 bytes as "KB" in many places. The discrepancy is why a 1 TB hard drive shows as ~931 GB in Windows: 1×10¹² bytes / 2³⁰ bytes-per-binary-GB ≈ 931. This converter uses decimal SI prefixes.
How precise are the conversions?
All conversions use IEEE 754 double-precision floating-point arithmetic, about 15–17 significant decimal digits. Where the underlying conversion factor is exact (1 inch = 2.54 cm, 1 mile = 1.609344 km, 1 lb = 0.45359237 kg), the only error is the floating-point rounding in the last digit, well below anything observable in practice. For everyday use, engineering estimates, homework and recipe scaling this is overkill in precision.
Why do months and years vary in length?
Calendar months range from 28 to 31 days; years from 365 to 366. For unit-conversion purposes most calculators (and this one) use averages, typically a "month" of 30.44 days (= 365.25 ÷ 12) and a "year" of 365.25 days (the Julian year, accounting for leap years on average). For precise duration arithmetic involving specific calendar dates, use a date calculator that knows about months, leap years and DST.
Does anything get sent to a server?
No. The conversion factors are baked into the page; the arithmetic is one multiplication or a small formula evaluated in JavaScript locally. Nothing about your input leaves the page; the tool works offline once it's loaded.