--- title: "Free Calculators and Converters in Your Browser" description: "13 free calculators and converters for units, currency, percentages, interest, dates, age, BMI, passwords and text, all running in your browser." url: "https://www.utillab.net/" language: "en" --- # Calculators and converters that run in your browser 13 free tools for units, currency, percentages, interest, dates, age, BMI, passwords and text. No sign-up, and what you type stays on your device. Looking for a calculator or converter? ## Try one now: percentage calculator [Open the percentage calculator](https://www.utillab.net/percentage-calculator) % Result — Formula: Result = (Percent ÷ 100) × Number ## Every tool, one index ### [Text to Speech Hot](https://savemetools.com/audio/text-to-speech/?utm_source=utillab&utm_medium=home) Natural voices, subtitles and multi-voice dialogues, with AI. ### [Unit Converter](https://www.utillab.net/unit-converter) Convert kilometers to miles, Celsius to Fahrenheit, and more. ### [Currency Converter](https://www.utillab.net/currency-converter) Convert between 70+ currencies at daily rates: ECB reference rates plus market rates for the rest. ### [Percentage Calculator](https://www.utillab.net/percentage-calculator) Find what percent of a number is, what percentage one value is of another, or calculate percentage change instantly. ### [Days Between Dates](https://www.utillab.net/date-difference) Count the days, weeks, months and business days between any two dates. ### [Age Calculator](https://www.utillab.net/age-calculator) Find your exact age in years, months and days, and the countdown to your next birthday. ### [Password Generator](https://www.utillab.net/password-generator) Generate strong, random passwords using your browser's cryptographic API. Choose length and character types. ### [Word Counter](https://www.utillab.net/word-counter) Count words, characters, sentences and reading time, and check social media and SEO limits. ### [BMI Calculator](https://www.utillab.net/bmi-calculator) Calculate your Body Mass Index in metric or imperial units and see your weight category instantly. ### [Convert Case](https://www.utillab.net/convert-case) Quickly change your text between various formats: all uppercase, all lowercase, etc. Take advantage of our character, sentence, paragraph, and line counters. ### [Advanced Calculator](https://www.utillab.net/advanced-calculator) Perform complex calculations with scientific functions and calculation history. ### [Simple Interest Calculator](https://www.utillab.net/simple-interest) Calculate simple interest per month or per year for loans and investments. ### [Compound Interest Calculator](https://www.utillab.net/compound-interest) Simulate how your money grows over time with compound interest. ### [Date Calculator](https://www.utillab.net/date-calculator) Find out what date it will be in the future or what date it was in the past. Perfect for planning and scheduling. What UtilLab is ## What you can do on UtilLab UtilLab has one main tool, a text to speech generator, and 13 small calculators and converters for everyday numbers, dates and text. This is how each part works. 1 ### Text to speech in 75 languages Paste a text, pick one of more than 300 neural voices in 75 languages and 142 accents, and adjust the speed and pitch. You can also write a dialogue with several voices and get subtitles timed to the speech. Your first audio is free without an account; to download the MP3 and make more audios each day, create a free account. 2 ### Calculators and converters that run in your browser The unit and currency converters, the percentage, scientific, compound interest, simple interest, date, days-between-dates, age and BMI calculators, the password generator, the case converter and the word counter all work on your device. What you type is not sent to our server; the currency converter only downloads the day's exchange rates. 3 ### Results you can check Each calculator shows how it reaches the result: the conversion factor, the interest formula with a year-by-year breakdown, the steps of the calculation. Calculations keep full precision and only the number shown is rounded, and each tool's guide explains the formula, its limits and the most common mistakes. UtilLab is free to use and is paid for by ads, which may appear on its pages; ads never change a result. The site is available in English, Portuguese and Spanish. It works on phones, tablets and computers, with a dark theme and keyboard search (Ctrl+K). ## Frequently Asked Questions ### Is UtilLab free? Yes. Every tool is free and there is no paid plan. The site is funded by ads, which may appear on its pages. Text to speech has a daily limit because each audio is generated on our server; the calculators and converters have no limit. ### Do I need an account? Not for the calculators and converters: they work right away, with no sign-up. In text to speech you can make one audio and listen to it without an account. To download the MP3 and generate more audios each day, create a free account with Google or an e-mail address. ### How does the text to speech work? Type or paste your text, choose a language and a voice, and press generate. The audio is synthesized on our server with Microsoft Edge neural voices: more than 300 voices in 75 languages and 142 accents. You can turn on subtitles (SRT or VTT) timed to the speech, or write a dialogue in which each speaker has a different voice. ### Is my text stored? The calculators and converters run in your browser, so what you type never reaches our server. Text to speech has to send your text to our server to create the audio; the file goes straight back to your browser and is not stored on the server. Your browser keeps your last 10 audios for 7 days, so download the ones you want to keep. ### Which calculators and converters are there? A unit converter, a currency converter with daily rates, a percentage calculator, a scientific calculator, compound and simple interest calculators, a date calculator, a days-between-dates counter, an age calculator, a BMI calculator, a password generator, a case converter and a word counter. They are available in English, Portuguese and Spanish. ### How accurate are the results? Unit conversions use the exact factors from international definitions, such as 1 inch = 2.54 cm, and the scientific calculator evaluates expressions with the math.js library. Results keep full precision and are rounded only when shown: up to 7 significant digits for units and 2 decimal places for money. Currency results use reference rates, so a bank or card will apply a slightly different rate. ### Which languages is the site available in? The whole site is available in English, Portuguese and Spanish. The voices cover 75 languages, so you can generate audio in a language the site itself is not translated into. ### Where is the text to speech tool? It is here, and also on SaveMeTools, our sister site, with the same voices, subtitles and dialogues. Its page asks first whether you'd rather open it on SaveMeTools: choose “Stay on UtilLab” and the question goes away, on this browser for good. ### Can I use UtilLab on my phone? Yes. The pages adapt to any screen size and nothing needs to be installed. Tools you mark as favorites, and the ones you used recently, appear at the top of the home page on that device. Last updated: November 13, 2026