Rounding Calculator

Understanding rounding for students and professionals

Rounding reduces a number’s digits while keeping it close to the original value. It’s essential in everyday math, budgeting, invoicing, engineering tolerances, lab measurements, and data reporting where readability and appropriate precision matter.

Common rounding methods

• Half up: If the next digit is 5 or higher, round up; otherwise round down. This is the classic approach taught in schools.
• Bankers (half to even): Exactly half cases round to the nearest even digit (e.g., 2.5 → 2, 3.5 → 4). Reduces cumulative bias in financial/data contexts.
• Floor: Always round down toward negative infinity (−2.1 → −3; 2.9 → 2).
• Ceiling: Always round up toward positive infinity (−2.1 → −2; 2.1 → 3).
• Truncate: Chop off extra digits toward zero (−2.9 → −2; 2.9 → 2). Fast and predictable, but not true rounding.

Rounding to decimal places vs significant figures

• Decimal places: Controls digits after the decimal (e.g., 123.456 → 123.46 at 2 decimal places).
• Significant figures: Controls total meaningful digits regardless of decimal position (e.g., 0.012345 at 3 sig figs → 0.0123).

Tie-breaking and fairness

When the next digit is exactly 5 followed by zeros, different rules apply. Half up always rounds up; bankers rounds to the nearest even, balancing results over time. Choose based on policy: schools favor half up; finance and statistics often prefer bankers.

Negative places: tens, hundreds, thousands

Use negative decimal places to round whole numbers to broader units: −1 → nearest ten (1,234 → 1,230), −2 → nearest hundred (1,234 → 1,200), and so on. This is useful for summarizing large volumes or anonymizing counts.

Best practices

• State your method: Document whether you used half up or bankers to avoid confusion.
• Match context: Financial reports often use two decimal places; scientific data uses significant figures aligned with measurement precision.
• Be consistent: Apply the same rules across a dataset for integrity.

Frequently asked questions

HOW TO use the rounding calculator?

Steps: Enter your number, choose “By decimal places” or “By significant figures,” select a method, and click Calculate. Copy the result if needed.

HOW TO round to the nearest tenth?

Select “By decimal places,” set Decimal places to 1, and choose your method (e.g., Half up). Enter the number and click Calculate.

HOW TO round to two decimals for invoices?

Set Decimal places to 2 and use Half up or Bankers depending on your accounting policy. This is standard for currency formatting.

HOW TO use bankers rounding (half to even)?

Choose Method = Bankers. Exact halves (like 2.5) round to the nearest even (→ 2), reducing cumulative bias in large datasets.

HOW TO round large counts to hundreds or thousands?

Enter a whole number and set Decimal places to a negative value: −2 for hundreds, −3 for thousands. Click Calculate to get the summarized figure.

HOW TO round using significant figures?

Select “By significant figures,” set the desired sig figs (e.g., 3), choose a tie method (Half up or Bankers), and calculate.

HOW TO format results for different countries?

Use the Output format menu (en-US, de-DE, fr-FR) to display commas, dots, or thin spaces according to locale conventions.

HOW TO embed this calculator on my website?

Copy this single-file HTML page into your project and link it from your navigation. You can also iframe it or integrate the JavaScript into your existing page.