102 free online tools that do the work in your browser — PDF converters, image editors and engineering calculators. Convert a PDF to Word, compress a file to an exact size, resize a photo, or size a resistor. Your files are never uploaded to a server, and nothing needs signing up for.
Search by name or browse by category — 102 tools across PDF, images, electronics, digital logic and health. Every one runs on your device.
Real answers, real visuals, zero friction. Everything you need, nothing you don't.
Diagrams, waveforms, and phasor plots update in real time as you type your values.
Every result includes the formula, substitution, and step-by-step calculation. Learn as you calculate.
No loading spinners, no accounts, no ads. Runs entirely in your browser — even without internet.
IPC-2152 trace sizing, E24 resistor values, datasheet LED voltages — results you can trust in real designs.
Numerical Calculator is a collection of 102 free tools covering three areas — document conversion, image editing and engineering calculation. What ties them together is architectural rather than cosmetic: every one of them runs entirely inside your browser. No file you open here is uploaded, stored on a server, or seen by anyone else.
That matters most for the converters. When you use a typical online PDF or image service, a complete copy of your document travels to infrastructure you do not control, is written to storage, processed, and held until a deletion job removes it. Several major services state this plainly in their own documentation. For a signed contract, a passport scan, a bank statement or an unpublished manuscript, the upload is the risk — not the conversion. Removing it removes the problem.
You can verify the claim rather than trust it: open any tool, disconnect from the internet, and use it. It still works.
Convert PDF to Word with tables rebuilt as real Word tables and images carried across, or pull out just the words with Extract Text from PDF, PDF to text and PDF to Markdown. Render pages as pictures with PDF to JPG, PDF to PNG or 300 DPI print output. Go the other way with JPG to PDF, PNG to PDF, combining images into one PDF or HEIC to PDF straight from an iPhone. Shrink files to an exact limit with Compress PDF — including dedicated 100 KB, 200 KB and 1 MB targets, plus scanned documents and email attachments. And bring documents together with Merge PDF, which lets you pick individual pages from each file.
The Image Studio does everything in one pass: crop, resize, compress and convert without saving between steps. Or use the focused tools — Image Compressor for an exact KB target, Image Resizer for precise dimensions (with ready-made pages for 1920×1080, 1280×720 and 1080×1080), Crop Image with aspect-ratio presets and exact pixel entry, and the Batch Image Converter for whole folders at once with a ZIP download. Single-format converters cover HEIC to JPG, JPG to PNG, PNG to JPG, JPG to WebP, SVG to PNG and more.
From the fundamentals of Ohm's Law, LED resistor sizing and resistor colour codes through RLC resonance, 555 timer design and buck and boost converters, to PCB trace width based on IPC-2152 and antenna gain. The digital logic set covers Karnaugh map solving, truth tables, Hamming codes, number system conversion and two's complement. Each shows the working, not just an answer.
BMI, BMR, body fat, calories and pregnancy due dates, plus EV versus petrol running costs and a CO₂ emissions calculator.
Each of these links straight to the tool that solves it:
“This PDF is too big to upload.” → Compress it to 200 KB, or use the email-limits guide if it is bouncing.
“I need to edit the text in this PDF.” → PDF to Word, which rebuilds tables and keeps headings.
“The portal wants one PDF, not eight files.” → Merge PDF, or combine photos into one PDF.
“I photographed my documents and need them as a PDF.” → JPG to PDF, or HEIC to PDF from an iPhone.
“I need this PDF page as an image for a slide.” → PDF to JPG, up to 600 DPI.
“My scan is enormous.” → Compress a scanned PDF — usually 70–90% smaller.
“The form says maximum 100 KB.” → Image Compressor with an exact KB target.
“My iPhone photos will not open on Windows.” → HEIC to JPG, or a whole album at once.
“I need a square profile picture.” → Crop Image with a 1:1 lock.
“This needs to be exactly 1920×1080.” → Resize to 1920×1080.
“I have forty photos to convert.” → Batch Image Converter, no file limit.
“My site is slow because of images.” → Bulk JPG to WebP.
“What resistor do I need for this LED?” → LED resistor calculator.
“What do these resistor bands mean?” → Resistor colour code.
“How wide should this PCB trace be?” → PCB trace width (IPC-2152).
“What R and C give me this 555 frequency?” → 555 astable calculator.
“Simplify this Boolean expression.” → Karnaugh map solver.
“Convert this to hex and two's complement.” → Number system converter.
Yes. Every one of the 102 tools is completely free, with no sign-up, no account, no email and no watermark. There are no daily limits and no paid tier.
No, and this is the single thing that unites every tool here. PDF conversion, image editing and compression all happen inside your browser using JavaScript. Your documents and photos never leave your device, are never stored on a server and are never seen by anyone. Most well-known online converters upload your files for processing; these do not.
Load any tool page, switch on airplane mode or disconnect your network, then use it. It still works, which is only possible because the processing is happening on your own computer or phone.
Convert PDF to Word, plain text or Markdown; convert PDF pages to JPG or PNG at up to 600 DPI; turn images into PDFs; compress a PDF to an exact size such as 100 KB or 200 KB; and merge or combine multiple PDFs with page-level control.
Convert between JPG, PNG, WebP, AVIF, GIF, BMP, HEIC and TIFF; compress images to an exact file size; resize to exact pixel dimensions; crop with aspect-ratio presets; and batch-convert many files at once with a ZIP download.
Electronics and circuits (Ohm's Law, LED resistors, resistor colour codes, power), reactive components and RLC resonance, 555 timers and DC-DC converters, PCB trace width and via design to IPC-2152, signal and antenna RF, digital logic (K-maps, truth tables, Hamming codes, number systems), plus health metrics and energy comparisons.
Yes. Every page is built for touch and small screens, including the crop tool and the drag-to-reorder controls in the PDF merger and image-to-PDF converter.
No. These are ordinary web pages - nothing is installed, no extension is required and no admin rights are needed.
They use the standard published formulas and, where relevant, industry references such as IPC-2152 for PCB trace width. Results are shown with the working so you can check them, and they are intended to support your own engineering judgement rather than replace it.
No artificial limits. Because processing runs on your own device, the practical constraint is your available memory rather than a policy set by us.