Useful References
Browse practical reference pages covering science, technology, measurements, countries, files, photography, energy, and everyday standards.
Battery Runtime Estimation Guide
Estimate runtime from watt-hours, load, efficiency, discharge limits, and battery chemistry.
Chemical Element Comparison Guide
Compare element families, states, conductivity, reactivity, and common uses.
Cooking Conversions and Substitutions
Common kitchen conversions, ingredient notes, and practical substitutions.
Country Codes, Currencies, and Time Zones
Compare codes, calling prefixes, currencies, and time zones for all 250 ISO-listed countries and territories.
CSS and Browser Compatibility Checklist
A practical checklist for resilient layouts across modern browsers and devices.
DNS Record Types Reference
Understand A, AAAA, CNAME, MX, TXT, CAA, NS, SOA, SRV, and PTR records.
Electrical Wire Size Reference
Compare AWG wire diameters, areas, copper resistance, and illustrative current guidance.
File Signatures and Magic Numbers
Identify common file formats from their opening hexadecimal bytes.
HTTP Status Codes and Security Headers
Reference common HTTP responses and the purpose of important browser security headers.
Large Number Scales Around the World
Understand billion, milliard, trillion, and the difference between short and long scales.
Paper and Envelope Sizes
Compare ISO A-series paper, common North American sheets, and envelope dimensions.
Photography Exposure and Depth of Field
Understand aperture, shutter speed, ISO, focal length, focus distance, and depth of field.
Solar Panel Output Estimation Guide
Estimate daily and annual solar generation from panel rating, sun hours, and system losses.
Unicode Latin Characters, Symbols, and Emoji Reference
Browse Latin-script letters and combining marks used across many languages, plus punctuation, symbols, and emoji.
World Currencies and Symbols
Reference currencies and symbols for all 250 ISO-listed countries and territories.