Rounding Calculator — quick guide
1) Core idea
Round a number to a chosen precision: decimal places, significant figures, or the nearest step (1, 10, 0.1, etc.).
2) How this tool works
- Decimal places: uses number.toFixed(n) for n digits after the decimal.
- Significant figures: rescales by powers of 10, rounds, then rescales back.
- Nearest value: rounds number/step with standard Math.round and multiplies back.
3) Sanity checks
- Input 3.14159 → 2 dp → 3.14.
- 1,234 → nearest 100 → 1,200.
- 0.0012345 → 3 significant figures → 0.00123.
4) Shortcuts that help
- Pick decimal places for currency; sig figs for measured data.
- Nearest value is great for bucketing (10s, 100s, 0.1s).
- Keep the unrounded source for further calculations.
5) Common pitfalls
- Halves round with JS Math.round rules (e.g., −1.5 → −1).
- Significant figures count leading zeros only after the first non‑zero digit.
- Avoid rounding multiple times; round once for display.
6) Micro-examples
- 12.3456, 3 dp → 12.346
- 9876, nearest 1000 → 10000
- 0.00999, 2 sig figs → 0.010
7) Mini-FAQ
- Negative numbers? Supported; rounding follows JS behavior.
- Banker’s rounding? Not used; this uses standard half-up via Math.round.
- Precision? Full double precision internally; output is formatted.
8) Action tip
Decide precision by context (finance vs. measurement) and round only at the presentation layer.