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.
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.
YouTube🎥YouTube ID Batch
Process many YouTube URLs with row-level errors and duplicate reporting.
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.