How rounding works
Find the place you are rounding to and look at the digit immediately to its right. If it is 5 or more, round up; if it is 4 or less, keep the digit and drop the rest. 3.14159 to two decimal places: the digit after the 4 is 1, so 3.14. 1234.5678 to the nearest hundred: the tens digit is 3, so 1,200.
Rounding modes
- Half up: the school method; 2.5 → 3, −2.5 → −3.
- Half to even (banker’s rounding): ties go to the nearest even digit, 2.5 → 2, 3.5 → 4. Used in IEEE 754 floating point and in many scientific and financial settings because it doesn’t bias totals upward.
- Up/down (ceiling/floor): always toward +∞ or −∞.
- Toward zero (truncate) and away from zero.
The calculator rounds the decimal digits exactly as typed, so it avoids floating-point surprises such as 1.005 rounding to 1.00.
Frequently asked questions
What is 2.45 rounded to one decimal place?
2.5 with half-up rounding; 2.4 with banker’s rounding (4 is even).
Should I round in the middle of a calculation?
No. Keep full precision until the final answer, then round once.