Round 123456 to 3 significant figures
The answer is 1.23 × 10⁵.
Significant figures
Non-zero digit. Every non-zero digit is significant.Zero between digits. A zero between two non-zero digits is significant.Leading zero. Leading zeros only fix the decimal point, so they are not significant.Trailing zero after the point. Trailing zeros in a number with a decimal point are significant.Trailing zero, no point. Trailing zeros in a number without a decimal point are not counted. Write 1.00 × 10² to make them count.Digit of a in a × 10ⁿ. In a × 10ⁿ every digit of a is significant, including its zeros. Counted and defined numbers, such as 3 coins or 100 cm in a metre, are exact and have unlimited significant figures.
Tap a digit to see why it counts.
6significant figures
Scientific notation1.23456 × 105
Round to
123456→1.23 × 10⁵Written as 123000 the trailing zeros are open to doubt.
The first dropped digit is 4, less than 5, so the last kept digit 3 stays.
Add, subtract, multiply, divide
Add or subtract. The answer keeps as many decimal places as the number that has the fewest. Multiply or divide. The answer keeps as many significant figures as the number that has the fewest. The rounding is done once, on the exact result.
- 4.2374 significant figures
- 2.513 significant figures
Exact result1.68804780876
Multiply or divide: keep the fewest significant figures.
Reported1.693 significant figures
Step by step
- 123456 has 6 significant figures. Keep the first 3: 1 2 3.
- The first dropped digit is 4, less than 5, so the last kept digit 3 stays.
- 123456 rounded to 3 significant figures is 1.23 × 10⁵.
More roundings
Counting instead? See the significant figures in 0.0025.
123456 to 3: quick answers
What is 123456 to 3 significant figures?
123456 to 3 significant figures is 1.23 × 10⁵. The first dropped digit is 4, less than 5, so the last kept digit 3 stays.
What if the dropped digit is exactly 5?
In the Class 11 rule, if the digit before it is even the 5 is dropped and nothing changes. If the digit before it is odd, that digit goes up by one. So 2.745 and 2.735 both become 2.74 to 3 significant figures.