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.
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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.
Image to PDF
The JPEG goes in unchanged and the page has a physical size. Which means the DPI is decided by how large you place it, not by the file.
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.