Three Decimal Places Rounding Tool

Enter Number

Common Examples: Rounding to Three Decimal Places

Original Number	Rounded to 3 Decimals	Explanation
3.14159265	3.142	Fourth decimal (5) rounds up
12.345678	12.346	Fourth decimal (6) ≥ 5, rounds up
0.123456	0.123	Fourth decimal (4) < 5, rounds down
99.9999	100.000	Rounds up to 100
7.8901234	7.890	Fourth decimal (1) < 5, rounds down
2.71828	2.718	Fourth decimal (2) < 5, rounds down

How to Round to Three Decimal Places

Rounding to three decimal places means keeping exactly three digits after the decimal point. This precision is widely used in scientific research, engineering calculations, financial analysis, and statistical studies where higher accuracy is required.

Why Round to 3 Decimal Places?

Scientific Accuracy: Standard precision for many lab measurements
Engineering: CAD, specifications, and technical drawings
Finance: Interest rates, exchange rates, and yield calculations
Statistics: Correlation coefficients, standard deviations, p-values
Chemistry: Molarity, pH, and concentration measurements

Step-by-Step Rounding Process

Step 1: Identify the Third Decimal Place

In the number 3.14159, the third decimal place is "1" (the thousandths position).

Step 2: Look at the Fourth Decimal

The fourth decimal digit determines rounding direction. In 3.14159, the fourth decimal is "5".

Step 3: Apply the Rounding Rule

If the fourth decimal is 5 or greater, round UP. If less than 5, round DOWN. Since 5 rounds up, result is 3.142.

Step 4: Keep Exactly Three Decimals

Drop all digits after the third decimal place. Final result: 3.142

Common Use Cases

Pi (π): 3.14159265... rounds to 3.142 for calculations

Euler's Number (e): 2.71828182... rounds to 2.718

Interest Rates: 4.5678% APR rounds to 4.568%

Measurements: 15.6789 cm rounds to 15.679 cm

Statistical Values: Correlation of 0.67891 rounds to 0.679

Academic & Professional Applications

Laboratory Work: Chemistry and physics lab reports typically use 3 decimals

Research Papers: Scientific journals often require 3 decimal precision

Engineering Design: Technical specifications and tolerance ranges

Financial Analysis: Bond yields, ratios, and performance metrics

Understanding Precision Levels

1 decimal place: Tenths (0.1) - basic precision

2 decimal places: Hundredths (0.01) - money, percentages

3 decimal places: Thousandths (0.001) - science, engineering

When to use 3 decimals: When you need more precision than 2 decimals but less than 4

Quick Reference

What is three decimal places? The thousandths position = 1/1000 = 0.001 precision

Key digit: Look at the fourth decimal place (ten-thousandths)

Standard use: Science, engineering, finance, and statistics