Small tools that
answer one question fast.
ecech. is a growing library of free, single-purpose online calculators and developer utilities. No signup, no clutter, no data collection — every tool runs entirely in your browser.
Popular right now
See all →Amazon FBA Calculator
Referral fee, fulfilment fee by size tier, monthly storage, returns and ad spend — subtracted in the order Amazon actually applies them, down to profit per unit.
E-commerce💻Base64 Encode / Decode
Text or files, both directions, with correct UTF-8 handling and a URL-safe toggle — plus the 33% size penalty shown before you paste a 4 MB image into a JSON payload.
Developer🏃BMI Calculator
Your BMI, your category, the healthy weight range for your height — and an honest account of the four situations where BMI gives the wrong answer about you.
Health✏️Case Converter
Nine cases including proper title case that leaves small words alone, plus the four naming styles developers switch between. Converts as you type.
Text & SEO💬CEFR to IELTS
Marks which mappings the test owners actually publish and which are guesses. There is no official IELTS-to-TOEIC conversion, and charts that give you one are inventing it.
English🌐CIDR to Subnet Mask
Every prefix from /0 to /32 with its netmask, wildcard, host count and binary. Handles /31 and /32, which the usual formula gets wrong.
NetworkBrowse 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.
Latest tools
New utilities ship every week.
PNG to JPG
Every transparent pixel has to become something. Choose the colour instead of letting the canvas default decide.
Image🎥YouTube Video ID
Paste any YouTube link — watch, youtu.be, embed, Shorts, live, with or without a playlist attached — and get the clean 11-character ID plus every other URL form.
YouTube🎥YouTube Title Length
See your title as it appears in mobile search, the home feed, a desktop watch page and a suggested sidebar — four different cut-off points, all of them shorter than 100.
YouTube🎥YouTube Thumbnail
Paste a link and see all six thumbnail sizes YouTube stores, at their real dimensions, with a direct download for each — plus the frame grabs most tools never show you.
YouTube🎥YouTube Repeat
Paste a link and it plays on repeat. Also explains why loop=1 on its own does nothing — the parameter almost every embed generator gets wrong.
YouTube🎥YouTube Link Cleaner
Paste a shared YouTube link and get back just the video. Explains which parameters are tracking, which change what the viewer sees, and which are safe to keep.
YouTube🎥YouTube Embed Code
Build the iframe with a live preview, get responsive CSS that will not break on mobile, and use the privacy domain that sets no cookies until the visitor presses play.
YouTube🎥YouTube A-B Loop
Set an in point and an out point, and the player repeats just that section forever — with adjustable speed for practising a guitar riff, a dance step or a language phrase.
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.