Practical browser tools
Practical tools that finish the job.
Free browser tools for real-world tasks — calculate, compare, validate, transform, plan and export.
What can you do here?
Move a real task forward
Popular right now
See all →1099 vs W-2
Going contract means picking up both halves of payroll tax, losing paid leave, and buying your own benefits. The rate has to move a long way to break even.
Finance💬Academic Tone Checker
Finds the casual words that cost marks in formal writing, with a replacement for each one — and leaves alone the things exam writing is supposed to have.
English🕑Date Calculator
Days are exact. Months clamp to the end of a shorter month and never come back, which is why monthly billing drifts after its first February.
Time🕑Age Calculator
Months are not a fixed length, so dividing days by 365.25 gives a different answer from the calendar. This uses the calendar method every official form uses.
Time🏠AC BTU Sizing
Dehumidifying needs sustained runtime. A unit that is too big hits the temperature target and shuts off before it has dried the air.
Home🎨Hex Opacity Calculator
Convert between hex alpha and percentage, and see the flat colour a semi-transparent layer actually produces over your background.
DesignBrowse by category
Ten focused collections, each built around a specific job to be done.
Financial & Currency
Currency conversion with real fees baked in, loan and interest maths, margin and payroll checks — the numbers that decide whether a deal is worth doing.
English Exams & Writing
Score conversions, writing checks and timing tools for IELTS, TOEFL and TOEIC — the parts of preparation that are arithmetic rather than practice.
Developer & Code
Formatters, validators, encoders and generators that save you from installing another dependency just to check one string.
Text & SEO Content
Counters, case converters, density analysers and readability checks for anyone whose words have to hit a limit or rank on Google.
Network & IP
Subnet maths, IP lookups, encoders and password generation — the sysadmin sidebar you keep open in a second tab.
Date, Time & Timezone
Timestamps, business-day maths and meeting windows that actually respect daylight saving in every city involved.
E-commerce & Pricing
Landed cost, marketplace fees, break-even discounting and ad profitability — pricing tools that subtract before they add.
Math & Statistics
Percentages, averages, deviation, significance and ratio maths, each with the working shown rather than just an answer.
Design & Color
Colour conversion, contrast auditing, palette building and CSS generators that output code you can paste straight into a stylesheet.
Health & Fitness
Body metrics, energy balance, hydration and pace calculators using published formulas, with the assumptions stated openly.
YouTube Creator Tools
Loop a section, pull a video ID out of any link, shift a whole subtitle file, build an embed — the small jobs that sit between filming and publishing.
Image & Photo Tools
Compress, convert, resize, crop and strip metadata entirely inside your browser. Your photos are never uploaded, because there is no server to upload them to.
Productivity & Units
Storage, speed, length, weight and paper-size conversion for the moments a spec sheet and your reality use different units.
Home & Construction
Material quantities, coverage rates and running costs for real projects — the waste factor, the rounding up to whole bags, and the units that quietly differ between the label and the job.
Latest tools
New utilities ship every week.
Waist-to-Hip Ratio
It is a ratio, so large hips hide a large waist. And one centimetre of tape placement moves the result by 0.01 — a category is only about 0.05 wide.
Health💻Invisible Characters
Finds zero-width spaces, bidi overrides and non-breaking spaces — and says which are harmless formatting and which are used to watermark or disguise text.
Developer📊Z-Score Percentile
Show left-tail percentile, upper tail and two-sided tail from one standard-normal z-score.
Math🎥Watch Time per 1K
Compare how efficiently impression opportunities become viewing time.
YouTube🎥Views per Viewer
Compare total views with YouTube's estimated unique audience for the same scope.
YouTube🎥Viewer Conversion
Normalize subscriber gains by views for comparable video-level analysis.
YouTube🎥Video Production Time
Build a realistic batch schedule from per-video work plus shared setup time.
YouTube🎥Length Deviation
Measure format difference without treating competitor duration as an ideal target.
YouTubeWhy ecech. exists
Most online calculators are the same three form fields wrapped in six advertisements and a cookie wall. They answer the textbook version of a question and ignore the version you actually have: not “what is 100 USD in euros” but “what will my card actually charge me after the foreign transaction fee”; not “what is 30% of 40” but “what discount can I run and still clear my target margin after marketplace fees”.
Every tool here is built around one of those realistic questions. Each one loads as a single self-contained page, runs entirely in your browser, keeps no account, sets no tracking cookie and sends none of your inputs to a server. Each one also shows its working — the formula, the assumptions and the edge cases — so you can check the result rather than trust it blindly.
- One job per page. No mega-calculator with 40 tabs.
- Real-world inputs. Fees, taxes, rounding and regional variants included where they matter.
- Shown working. Formulas and assumptions are printed next to the answer.
- Fast everywhere. Single file, no framework, usable on a phone on bad hotel wifi.