How to Round Numbers, Step by Step (With Examples)

A MathHelp247 guide · Rounding · Grades 3–6

Rounding replaces a number with a simpler one that's close in value. The rule is the same whether you're rounding a big whole number or a decimal: find the rounding place, check the digit to its right, and round up or down.

The three steps

1. Find the rounding place — the ten, hundred, tenth, and so on that you've been asked to round to.
2. Look at the digit just to its right — this is the "decider".
3. Round: if the decider is 5 or more, round up; if it's 4 or less, round down (leave the rounding digit the same).

Worked example 1: 3,476 to the nearest hundred

Worked example 2: 5.78 to the nearest tenth

The tricky case: rounding up causes a carry

Sometimes rounding up rolls over into the next place. To round 97 to the nearest ten, the decider is 7, so we round up — but 9 tens plus 1 makes 10 tens, which is 100. So 97 ≈ 100. Just treat it like carrying in addition.

Common mistakes to avoid

• Looking at the wrong digit. Only the single digit immediately to the right decides — not all the digits after it.
• Forgetting the placeholders. When rounding whole numbers, the places after the rounding place become zeros, not nothing.
• Rounding twice. Round in one move using the original decider; don't round the decider first.

Why rounding matters

Rounding is how we estimate to check whether an answer is reasonable. It builds on place value — you have to know which digit sits in the tens, hundreds or tenths place before you can round to it.