Rounding Calculator
Round a number to any number of decimal places, up or down.
Results update as you type.
About this calculator
A rounding calculator rounds a number to a chosen number of decimal places (or significant figures) and shows four results side by side: the standard nearest-value rounding, always-up (ceiling), always-down (floor), and truncation, so you can compare every option at once.
Standard rounding looks at the digit just past the cut-off — 5 or more rounds up, less than 5 rounds down — so 3.14159 to two decimal places is 3.14. The other columns force a direction: for 2.673 the nearest and floor both give 2.67 while the ceiling gives 2.68, and truncation simply drops the extra digits to 2.67 without rounding. Switching the mode to significant figures counts meaningful digits from the first non-zero one instead, and a negative number of places rounds to the left of the point, so 3457 to −2 places becomes 3500.
Rounding matters for money, measurements, reporting to a sensible precision, and avoiding false accuracy in results. Seeing nearest, up, down and truncated together makes it clear how much a value shifts depending on which rule you apply.
Frequently asked questions
How does rounding to decimal places work?
Look at the digit just past the cut-off: 5 or more rounds up, less than 5 rounds down. 3.14159 to two places is 3.14.
What does a negative number of decimal places do?
It rounds to the left of the decimal point: −1 rounds to the nearest ten, −2 to the nearest hundred. 3457 to −2 places is 3500.
What is the difference between rounding up and rounding down?
Rounding up (ceiling) always moves to the larger value and rounding down (floor) to the smaller, while nearest picks whichever is closer. For 2.673 to two places, nearest and down give 2.67 but up gives 2.68.
What does the truncated result show?
It cuts off the digits beyond your chosen place without rounding at all. 2.673 truncated to two decimal places is 2.67, even though nearest rounding also gives 2.67 here and 2.678 would truncate to 2.67 while rounding to 2.68.
How do I round to significant figures instead of decimal places?
Switch the mode from decimal places to significant figures. A precision of 3 then keeps the first three meaningful digits, so 0.0045213 becomes 0.00452.
Does rounding up always make a number bigger?
Only for positive numbers. Rounding up means toward positive infinity, so −2.7 rounded up to a whole number is −2, which is larger, not smaller.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/rounding/curl
curl "https://calculator.free/api/v1/rounding/?number=3.14159&places=2&mode=decimals"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/rounding/?" + new URLSearchParams({
"number": "3.14159",
"places": "2",
"mode": "decimals"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.