Rounding tool

Commas, currency symbols and a trailing % are ignored, so pasted values just work.

Try one
0 decimal places
modes disagree

Original

2.5

Rounded (half up)

3

This value sits on a tie, so the rounding rule changes the answer. Compare them below.

Every rounding ruledifference from the original

Half up

Ties go away from zero for positives — the school rule

3+0.5

Half to even

Banker’s rounding: ties go to the even digit

2-0.5

Half away from zero

Ties always move away from zero

3+0.5

Half toward zero

Ties always move toward zero

2-0.5

Ceiling

Always up, toward +∞

3+0.5

Floor

Always down, toward −∞

2-0.5

Truncate

Drops the extra digits without rounding

2-0.5

Nearest 0.25

Snapped to the closest step

2.5exact

Down to 0.25

Snapped down to the step below

2.5exact

Up to 0.25

Snapped up to the step above

2.5exact
Original2.5
Half up3
Half to even2
Truncated2

Numbers

Back to the tool

Number Rounding Tool

Compare common rounding rules before committing to one. Round by decimal places, significant figures, or a custom step, and see half-up, half-even, floor, ceiling, truncation, and directional tie rules side by side.

Rounding methods compared
8
Decimal-place range
−6…10
Magnitude-aware precision
Sig figs
Custom increments
Step

Step by step

How to use it

  1. 01

    01Enter the unrounded value

    Keep all known digits; rounding early can compound error in later calculations.

  2. 02

    02Set decimal places

    Positive places round after the decimal point; negative places round tens, hundreds, and beyond.

  3. 03

    03Compare the rules

    Pay particular attention to exact halfway values and negatives, where familiar methods disagree.

  4. 04

    04Choose a precision with meaning

    Use significant figures for measured precision or a step for prices, intervals, and allowed increments.

Worked example

The awkward case: 2.5

Given

Value
2.5
Places
0

Methods disagree at the tie

half up       3
half even     2
ceil          3
floor         2
truncate      2
away from 0   3
Nearest choices
2 or 3
Half-even
2
Half-up
3

Both nearest rules are defensible; consistency matters. Half-even reduces aggregate upward bias when many independent ties are rounded.

Why this one

Rounding is a policy, not just formatting

Halfway values expose the rule

Most values have one nearest choice. Exact ties require a declared direction, so different systems can produce different correct answers.

Floor is not truncation

For −2.3, floor is −3 while truncation is −2. They agree only for positive values.

Significant figures follow magnitude

Three significant figures means 12,300 for 12,345 but 0.0123 for 0.012345.

Display precision is not measurement accuracy

Adding decimal places cannot make an imprecise source more accurate; it only changes how the result is written.

The judgement call

Which rounding rule fits?

  • A general one-off display

    Half up

    It matches the rule most people were taught.

  • Many financial or statistical values

    Half even

    It reduces systematic drift across repeated ties.

  • Never exceed a capacity

    Floor

    The rounded result stays at or below the value.

  • Count complete units only

    Truncate

    It removes the fractional part toward zero.

Reference

The numbers behind it

Decimal places
Position relative to decimal point
Significant figures
Digits from first non-zero
Half even
Tie goes to the even neighbor
Step rounding
round(value / step) × step

FAQ

Questions, answered plainly

What is banker's rounding?

Banker's rounding is half-even: an exact halfway value goes to the nearest even last digit. Thus 2.5 becomes 2 and 3.5 becomes 4.

How do negative decimal places work?

They round digits left of the decimal point. Minus one rounds to tens, minus two to hundreds, and so on.

What is the difference between floor and truncate?

Floor moves toward negative infinity; truncate moves toward zero. For positive values they match, but for negative non-integers they differ.

When should I use significant figures?

Use them when precision depends on the scale of a measurement rather than a fixed number of digits after the decimal point.

Why can decimal rounding look surprising in software?

Many decimal fractions cannot be represented exactly in binary floating point. The tool scales values carefully, but source-number representation can still matter at extreme precision.

Rounding and comparisons run entirely in your browser.

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