Skip to content
Eight categories · Every unit at once

Unit Converter metric, imperial, US

Type one value and see it in every unit of its family — not only the pair you picked. Handy when a recipe, a plan or a datasheet speaks another measurement system.

Short answerLast edited October 31, 2026

The Unit Converter switches between metric and imperial units for length, weight, temperature, area, speed and data, and shows the exact factor it uses. For example, 1 inch equals exactly 2.54 centimetres, with no rounding error in the definition.

How it works

1

Enter the value

Add the number you want to convert.

2

Pick the units

Choose length, weight, temperature and the two units.

3

Read the conversion

The converted value appears as you type.

Two systems, one world

LosslessMetric

Metre, kilogram, litre, Celsius. Powers of ten everywhere — convert by moving the decimal point.

LosslessImperial

Inch, foot, pound, pint (UK), Fahrenheit. Built from historical objects, so the factors are odd numbers.

LossyUS customary

Looks like imperial, is not: a US pint is 16 fluid ounces, a UK pint is 20. Recipes notice.

Factors worth memorising

FromToExact factor
1 inchcentimetres2.54
1 footcentimetres30.48
1 milekilometres1.609344
1 kilogrampounds2.20462262
1 litreUS fluid ounces33.814023
1 US gallonlitres3.785412
1 knotkm/h1.852
°F to °Ctemperature(°F − 32) × 5 ÷ 9
Are the factors exact?
Yes. Inch, pound and litre definitions are fixed by international agreement, so the conversions are exact to the decimals shown.
Which gallon do you use?
The US gallon, 3.785412 litres. A UK imperial gallon is 4.54609 litres and is not in the list.
How many decimals are shown?
Up to four significant places, or scientific notation for very small and very large results.
Can I convert file sizes?
Yes, in the File size category, in both decimal (MB) and binary (MiB) units. This matters when a disk is advertised in one and reported in the other.
Does it work offline?
Yes. The conversions are plain arithmetic inside the page, with no network call.

A Short History of Measuring Things Badly

Before the metre there were feet — quite literally, the king's. That is why a foot was between 25 and 34 centimetres depending on where you stood.

The metre and the kilogram

The French revolutionary metre was meant to be one ten-millionth of the distance from the pole to the equator. The kilogram was a lump of platinum in a vault near Paris, until 2019, when it was redefined through the Planck constant so that nobody has to dust it.

The inch that was agreed on

In 1959 the English-speaking world signed the same definition: 25.4 millimetres exactly. Every conversion on this page rests on that agreement, which is why inch and pound results are exact rather than close.

Where the mistakes happen

Aviation lost a Mars orbiter to a metric-imperial mix-up in 1999, and a Boeing 767 once ran out of fuel because a fuel load was calculated in pounds and loaded in kilograms. When a number crosses a system, write the unit next to it — every time.

If a measurement is about media rather than the physical world, the video size calculator and image compressor deal in the same kind of arithmetic.

More free tools

Video to Audio ExtractorSave the sound of MP4, MOV and WebM videos as MP3 right in your browser.No uploadFreeOpen tool Audio Format ConverterBatch convert between MP3, WAV, M4A, FLAC, OGG and OPUS.No uploadFreeOpen tool MP3 Cutter & Ringtone StudioTrim any part of a song, add fades and make a ringtone.No uploadFreeOpen tool Audio MergerCombine several audio files into one track with smooth transitions.No uploadFreeOpen tool Audio Loudness BoosterMake quiet recordings louder and normalize them to a standard level.No uploadFreeOpen tool Slowed + Reverb StudioCreate slowed + reverb, sped up and nightcore versions of songs.No uploadFreeOpen tool Background Noise RemoverClean hum, fan and traffic noise from voice recordings.No uploadFreeOpen tool Pitch ShifterRaise or lower the pitch by up to an octave and keep the running time exactly as it was.No uploadFreeOpen tool Silence RemoverCut the dead air out of interviews, lectures and voice notes and see how much shorter the file gets.No uploadFreeOpen tool Audio EqualizerCut mud, lift speech and add air with a 10-band equalizer and six presets.No uploadFreeOpen tool Audio Reverb EffectAdd room, studio, hall or plate space with control over decay and wet mix.No uploadFreeOpen tool Audio Chorus EffectDouble a take with two or three drifting voices and stereo width.No uploadFreeOpen tool Audio Fade In/OutWrite smooth fade ins and fade outs of any length into the file itself.No uploadFreeOpen tool Stereo to Mono ConverterFold stereo to mono, keep one channel or swap left and right.No uploadFreeOpen tool Audio NormalizerEven out volume with peak or average normalization and a no-clip safety.No uploadFreeOpen tool Video Caption MakerCreate captions with AI or use an SRT file and burn them into the video.No uploadFreeOpen tool Video to Text ConverterTurn the speech of videos and recordings into text and SRT subtitles.No uploadFreeOpen tool AI Video Summary GeneratorGet the summary, chapters and notes of long videos, lectures and podcasts.AIFreeOpen tool Video Size ReducerShrink a video to the size you need for Discord, email or WhatsApp.No uploadFreeOpen tool GIF Maker & Video CutterCut part of a video and save it as a GIF or a shorter MP4.No uploadFreeOpen tool Vertical Video ConverterTurn 16:9 videos into 9:16 vertical format with a blurred background.No uploadFreeOpen tool Video Frame ExtractorSave any frame of a video as a full-resolution image.No uploadFreeOpen tool Video Metadata ViewerSee the resolution, bitrate, codec and FPS of a video file.No uploadFreeOpen tool AI Clip MakerAI finds the best moments of a long video and turns them into captioned vertical clips.AIFreeOpen tool AI Video EnhancerEnhance video quality, upscale resolution and reduce noise with AI.AIFreeOpen tool Auto Captions GeneratorGenerate accurate captions and subtitles for videos automatically.AIFreeOpen tool Smart Video TrimmerTrim videos with frame-accurate precision in your browser.No uploadFreeOpen tool Video Loop MakerCreate seamless looping videos for GIFs and social media.No uploadFreeOpen tool VTT Subtitle GeneratorGenerate WebVTT subtitle files from video transcripts.No uploadFreeOpen tool Video CropperCrop videos to focus on important areas or change aspect ratio.No uploadFreeOpen tool Image Format ConverterConvert between JPG, PNG and WebP and shrink the file with a quality slider.No uploadFreeOpen tool Social Image ResizerFit photos to Instagram, YouTube, TikTok and X sizes in one click.No uploadFreeOpen tool HEIC Photo ConverterBatch convert iPhone HEIC photos to JPG or PNG.No uploadFreeOpen tool EXIF & GPS RemoverDelete the GPS location and camera data of a photo before you share it.No uploadFreeOpen tool Watermark MakerAdd your @handle or logo to photos and videos.No uploadFreeOpen tool Instagram Grid & Carousel MakerSplit a wide photo into a seamless carousel or a profile grid.No uploadFreeOpen tool AI Video Idea FinderTen filmable video ideas with a hook and a reason, plus three series concepts.AIFreeOpen tool AI Title & Tag WriterWrite titles, descriptions and tags for YouTube, TikTok, Reels and more.AIFreeOpen tool AI Caption & Bio WriterCaptions, hashtag sets and bios that fit every platform limit.AIFreeOpen tool AI Hook & Script WriterHooks that grab viewers in the first second and timed shooting scripts.AIFreeOpen tool AI Channel Name IdeasMemorable name ideas for Instagram, TikTok, YouTube, X and Twitch.AIFreeOpen tool AI Meta Description GeneratorWrite title tags and meta descriptions that fit Google and earn the click.AIFreeOpen tool AI Product Description WriterTurn a spec sheet into three product descriptions, benefit bullets and search phrases.AIFreeOpen tool AI Blog Outline GeneratorPlan an article that answers the search: headlines, headings, word budget, FAQ and internal links.AIFreeOpen tool AI Podcast Show Notes GeneratorTurn an episode transcript into a summary, six takeaways, chapters, quotes, titles and tags.AIFreeOpen tool AI Text RewriterRewrite a text shorter, simpler, more formal or more persuasive, and see exactly what changed.AIFreeOpen tool AI TranslatorTranslate between seven languages and keep the register: formal, neutral or informal.AIFreeOpen tool AI FAQ GeneratorWrite the questions customers actually ask, with answers, follow-ups and FAQ schema for the page.AIFreeOpen tool AI Storyboard GeneratorTurn an idea into a timed shot list you can film alone: framing, action, on-screen text and voiceover.AIFreeOpen tool Social Keyword FinderFind the phrases and questions people search inside Instagram, TikTok, YouTube and Pinterest.AIFreeOpen tool Image CompressorShrink photos to a target size for a form, an email or a shop page, without leaving the browser.No uploadFreeOpen tool Favicon & App Icon GeneratorMake every icon a site needs: 16 to 512 pixels, a real favicon.ico and the HTML to paste.No uploadFreeOpen tool Image CropperCrop a photo to a social size, a cover or a profile picture by dragging the frame.No uploadFreeOpen tool Image to PDFTurn photos and scans into one PDF: page size, orientation, margin and page order.No uploadFreeOpen tool Passport & ID Photo MakerCrop a photo to passport, visa or ID sizes with a head-height guide and print it on one sheet.No uploadFreeOpen tool Meme GeneratorPut a caption on any picture: four layouts, outlined type and a square export for every feed.No uploadFreeOpen tool AI Background RemoverRemove backgrounds from images instantly with AI.AIFreeOpen tool AI Image UpscalerUpscale images up to 4x while enhancing details with AI.AIFreeOpen tool AI Object RemoverErase unwanted objects, people or text from photos.AIFreeOpen tool AI Image GeneratorCreate stunning AI images from text prompts in seconds.AIFreeOpen tool AI Avatar GeneratorGenerate unique AI avatars from photos or text descriptions.AIFreeOpen tool AI Logo GeneratorGenerate a logo mark from a description and set your brand name in type, ready for a PNG.AIFreeOpen tool Image to Text OCRExtract text from images and scanned documents with high accuracy.AIFreeOpen tool Color Palette ExtractorExtract color palettes from any image automatically.No uploadFreeOpen tool Face Blur ToolAutomatically blur faces in photos for privacy protection.No uploadFreeOpen tool WebP Image ConverterConvert images to and from WebP format for better web performance.No uploadFreeOpen tool Image to Video MakerTurn photos into a slideshow video with pan, zoom and crossfades.No uploadFreeOpen tool AI Blog WriterGenerate complete blog posts with SEO optimization in seconds.AIFreeOpen tool AI Article GeneratorCreate high-quality articles on any topic with AI assistance.AIFreeOpen tool AI Email WriterWrite professional emails for any purpose instantly.AIFreeOpen tool AI Ad Copy GeneratorGenerate compelling ad copy for Google, Facebook, and more.AIFreeOpen tool AI Product Review GeneratorCreate authentic product reviews for any item.AIFreeOpen tool AI SEO Content WriterWrite SEO-optimized content that ranks higher on search engines.AIFreeOpen tool AI ParaphraserRephrase text while maintaining meaning and tone.AIFreeOpen tool AI Grammar CheckerFix grammar, spelling, and punctuation errors instantly.AIFreeOpen tool AI Resume BuilderCreate professional resumes tailored to any job.AIFreeOpen tool AI Cover Letter WriterWrite personalized cover letters for job applications.AIFreeOpen tool AI Business Name GeneratorFind the perfect name for your business or brand.AIFreeOpen tool AI Slogan GeneratorCreate catchy slogans and taglines for your brand.AIFreeOpen tool AI Hashtag GeneratorGenerate trending hashtags for social media posts.AIFreeOpen tool AI Question GeneratorCreate quiz questions and study materials with AI.AIFreeOpen tool AI Testimonial GeneratorGenerate authentic customer testimonials for your business.AIFreeOpen tool AI Press Release GeneratorWrite professional press releases in minutes.AIFreeOpen tool AI LinkedIn Post GeneratorCreate engaging LinkedIn posts that drive engagement.AIFreeOpen tool AI Twitter Thread GeneratorTurn ideas into viral Twitter/X threads.AIFreeOpen tool AI Poem GeneratorGenerate beautiful poems for any occasion.AIFreeOpen tool PDF MergerCombine several PDFs into one file, in the order you choose.No uploadFreeOpen tool PDF SplitterExtract page ranges from a PDF or save every page as its own file.No uploadFreeOpen tool PDF CompressorMake a heavy PDF small enough to send, without uploading it.No uploadFreeOpen tool PDF to Image ConverterSave every page of a PDF as a JPG or PNG at screen, print or 300 dpi quality.No uploadFreeOpen tool PDF Page OrganizerRotate, delete and reorder the pages of a PDF, then save one clean new file.No uploadFreeOpen tool Sign a PDFDraw or upload your signature, place it on the page and download the signed PDF.No uploadFreeOpen tool Unlock PDFRemove password protection from PDF files.No uploadFreeOpen tool Protect PDFAdd password protection to PDF files.No uploadFreeOpen tool Rotate PDF PagesRotate PDF pages individually or all at once.No uploadFreeOpen tool BMI CalculatorCalculate Body Mass Index and healthy weight range.No uploadFreeOpen tool Calorie CalculatorCalculate daily calorie needs based on age, weight, and activity.No uploadFreeOpen tool Loan CalculatorCalculate loan payments, interest, and amortization.No uploadFreeOpen tool Mortgage CalculatorCalculate mortgage payments and total interest.No uploadFreeOpen tool Percentage CalculatorCalculate percentages, increases, and decreases easily.No uploadFreeOpen tool Age CalculatorCalculate exact age in years, months, and days.No uploadFreeOpen tool Unit ConverterConvert between length, weight, temperature, and more.No uploadFreeOpen tool Tip CalculatorCalculate tips and split bills easily.No uploadFreeOpen tool Discount CalculatorCalculate discounts, sale prices, and savings.No uploadFreeOpen tool BMR CalculatorCalculate Basal Metabolic Rate and TDEE.No uploadFreeOpen tool Video Bitrate CalculatorTurn a target file size and a running time into the bitrate to export with.No uploadFreeOpen tool Video Size & Upload TimeSee how big a video will be, which apps accept it and how long the upload takes.No uploadFreeOpen tool Aspect Ratio CalculatorConvert 16:9, 9:16, 4:5 and any custom ratio into exact pixel sizes.No uploadFreeOpen tool Cool Text GeneratorBold, italic, script and 20+ text styles to copy into bios and captions.No uploadFreeOpen tool Social Character CounterCount characters, hashtags and emojis against every platform limit.No uploadFreeOpen tool Creator Earnings CalculatorEstimate ad and sponsorship income on YouTube, TikTok and Instagram.No uploadFreeOpen tool Sponsorship Rate CalculatorTurn followers, views, engagement and niche into a price range to quote a brand.No uploadFreeOpen tool Engagement Rate CheckerCalculate your engagement rate and compare it with typical rates.No uploadFreeOpen tool YouTube Thumbnail TesterSee how your thumbnail and title look on the YouTube home page and on phones.No uploadFreeOpen tool Vertical Video Safe Zone CheckerCheck that text and faces are not hidden under the app buttons.No uploadFreeOpen tool CTR CalculatorCalculate click-through rates and optimize campaigns.No uploadFreeOpen tool CPM CalculatorCalculate cost per mille and campaign costs.No uploadFreeOpen tool CPC CalculatorCalculate cost per click for advertising campaigns.No uploadFreeOpen tool ROI CalculatorCalculate return on investment for campaigns.No uploadFreeOpen tool RPM CalculatorCalculate revenue per mille for content monetization.No uploadFreeOpen tool Hashtag Performance CalculatorAnalyze hashtag performance and reach potential.No uploadFreeOpen tool Best Posting Time CalculatorFind optimal posting times for maximum engagement.No uploadFreeOpen tool Influencer Value CalculatorCalculate your influencer marketing value.No uploadFreeOpen tool Content Value CalculatorEstimate the monetary value of your content.No uploadFreeOpen tool Collaboration Rate CalculatorCalculate fair rates for brand collaborations.No uploadFreeOpen tool

Quick facts

  1. An inch is exactly 25.4 mm and a pound exactly 0.45359237 kg, so these conversions are exact by definition rather than approximate.
  2. Temperature is the exception: degrees Celsius and Fahrenheit differ by an offset as well as a factor, so they cannot be converted by multiplying alone.
  3. The SI defines the kilo as exactly 1000 and the centi as exactly one hundredth, which is why conversions are exact, not approximate.BIPM
  4. Since 2019 the kilogram is defined by a fixed value of the Planck constant, not by a metal cylinder in Paris.BIPM

Questions people ask

How many centimetres are in an inch?
Exactly 2.54 centimetres. The inch has been defined as 25.4 millimetres since the international yard and pound agreement of 1959, so the conversion is exact.
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9, divide by 5 and add 32. So 20 °C is 20 × 9 ÷ 5 + 32 = 68 °F. The reverse is to subtract 32, multiply by 5 and divide by 9.
What is the difference between a kilogram and a pound?
A kilogram is the SI base unit of mass, and a pound is defined as exactly 0.45359237 kilograms. A 70 kg person weighs about 154.3 pounds, and weight in pounds is mass in kilograms divided by 0.45359237.

What this page is about

  • SI units

    The International System of Units maintained by the BIPM, with the metre, kilogram, second and their prefixes defined exactly.

Official sources cited on this page

  1. The International System of Units (SI Brochure)BIPM

Keep going with the next tool

The tools in this group that do the next piece of the same work, all switched on right now.

BMI CalculatorCalculate Body Mass Index and healthy weight range.No uploadFreeCalorie CalculatorCalculate daily calorie needs based on age, weight, and activity.No uploadFreeLoan CalculatorCalculate loan payments, interest, and amortization.No uploadFreeMortgage CalculatorCalculate mortgage payments and total interest.No uploadFree

Switched-off tools are not listed here: only what works right now.

How would you rate Unit Converter?Be the first to rate it