免費線上工具

Find the moon phase for any date — new moon, full moon, quarters, and crescents. Shows illumination %, moon age, and days to next new or full moon. Free, browser-based.

Calculate cosmological redshift from wavelengths or recession velocity. Convert z to velocity, Hubble distance, and scale factor. Free, browser-based astronomy tool.

Calculate Richter magnitude from seismograph amplitude and distance, explore effects and energy for any ML value, or compare two magnitudes. Free, browser-based.

Calculate heat index (feels-like temperature) from air temperature and relative humidity. Uses the official NWS Rothfusz formula with heat risk guidance. Free, browser-based.

Calculate air density from temperature, pressure, and humidity, or from altitude. Shows kg/m³, virtual temperature, speed of sound, and comparison to sea-level standard. Free, browser-based.

Calculate bolt tightening torque, clamp preload, and nut factor K. Modes: torque from preload (T = KDF), preload from torque, recommended torque from proof load and bolt grade, and nut-factor solver. Metric (mm, kN, N·m) and imperial (in, lbf, lbf·ft) with M6–M24 and Grade 5/8 presets. Free, browser-based.

Graph mathematical functions y = f(x) instantly. Enter expressions like sin(x), x^2, exp(x), or multiple functions — get an SVG plot with axes, grid, and auto-scaling. Free, browser-based.

Convert PDF pages to JPG images in your browser with adjustable quality and resolution.

Combine multiple PDF files into one document in your browser, with drag-free reordering and instant download.

Add password protection and permission restrictions to PDF files entirely in your browser.

Draft professional emails with AI using your own OpenAI, Anthropic, Google, or Groq API key.

Generate SEO-friendly blog posts with title, meta description, and markdown content using your own AI API key.