23 free calculators for home energy and electronics. Size a solar system from your bill, see how long a battery will run, estimate appliance running costs, plan EV charging, or pick a wire size with voltage drop. For makers and engineers: resistor colour codes, LED resistors, voltage dividers, RC filters, 555 timers, PCB trace width, plus FPGA clock, CRC and FIFO tools. Every result shows the formula and a worked example. No sign-up, and any calculator embeds in a blog.
Make passport, visa and ID photos that meet official size rules, for free. Pick a country and document, upload a phone photo, and it finds your face, crops to the exact spec and replaces the background. Download a JPEG under the portal's size limit, or a 4x6 in / A4 print sheet. Everything runs in your browser, so your photo is never uploaded. No sign-up, no watermark. Covers the US, UK, Schengen, Canada, India, Pakistan, China, Australia and more.
