Coin Collection Start

Simple in-browser notepad with auto-save. Write quick notes that persist in your browser. Download as text file. No signup needed.

Calculate percentages in seven modes with visible formulas, strict input validation, signed percentage change, and symmetric percentage difference.

Project deterministic investment growth from a starting value and monthly contributions, with explicit beginning- or end-of-month timing and dollar reconciliation.

Compress images client-side with no server upload. Adjust quality, max width, and output format. Compare before/after and download compressed images.

Score inclusion severity from count, average size, and visibility position. Free inclusion grading score tool for inclusion, grading, and more.

Convert gemstone weight between carats and grams. Essential jewelry making tool for planning, budgeting, and project optimization.

Calculate Gregorian calendar age and UTC-stable elapsed days between two dates, with an explicit February 29 countdown rule and labeled illustrative context.

Project a starting balance and real month-end contributions under annual, semiannual, quarterly, monthly, or daily nominal compounding, with exact deposit and interest reconciliation.

Calculate elapsed clock time from strict 24-hour readings with an explicit same-day or next-day choice and auditable seconds.

Calculate a strict calendar difference, elapsed days, inclusive dates, completed months, and Mon–Fri dates without DST off-by-one errors.