How to use the ROUNDDOWN function
What is the ROUNDDOWN function?
The ROUNDDOWN function calculates a number rounded down based on the number of digits to which you want to round the number.
1. Introduction
How to round numbers?
Rounding is a method to simplify a number by reducing its digits while keeping its approximate value close to the original value.
There are a few common ways to round:
-
- Round to a set number of decimal places, rounding 2.13579 to 2 decimal places gives 2.14.
- Round up or down to the nearest integer, rounding up 2.3 gives 3. Rounding down 2.3 gives 2.
- Round to a set increment, rounding to the nearest 10 rounds 17 to 20.
- Round to significant figures, rounding 2.333 to 3 significant figures gives 2.33.
When rounding, look at the first digit after where you want to round. If it's 5 or more, round up. If less than 5, round down. Rounding makes numbers cleaner and easier to work with in many everyday situations, however, they may also cause rounding errors like rounded values can compound errors. Rounding measurements and constants may reduces precision. It is better to round numbers after performing calculations than before.
What is a decimal place?
A decimal place refers to each position held by a digit in a number. The first decimal place is the tenths place (1/10), the second is the hundreds place (1/100) and so on.
What is a comma?
Commas are frequently used in large numbers to help read and interpret the values easier. Commas separate thousands place values in large numbers. For example:
- 10,000 - ten thousand
- 100,000 - one hundred thousand
- 1,000,000 - one million
The comma creates groups of three digits, making it easier to count the zeroes and understand the scale.
In decimal numbers with both whole and fractional parts, commas separate the whole number groups of three digits. For example:
- 3,421.256
- 102,734,221.985
What is an integer?
An integer is a whole number that can be positive, negative, or zero, but not a fraction or decimal.
What other Excel functions round numbers?
| ROUND | Rounds a number to a specified number of digits |
| ROUNDUP | Rounds a number up, away from zero |
| ROUNDDOWN | Rounds a number down, towards zero |
| MROUND | Rounds a number to the nearest multiple of a specified value |
| CEILING | Rounds a number up to its nearest multiple. |
| ODD | Returns number rounded up to the nearest odd integer. |
| EVEN | Rounds a number up to the nearest even whole number. |
| FIXED | Rounds a number to the specified number of decimals, lets you ignore comma separators. |
Formula in cell C3:
Formula in cell D3:
2. Syntax
ROUNDDOWN(number, num_digits)
| number | Required. The value to round. |
| num_digits | Required. A number representing the digit you want to round down to. |
The ROUNDDOWN function rounds
- down to the given decimal if num_digit is larger than 0 (zero).
- down to the nearest integer if num_digit is 0 (zero).
- down to the number to the left of the decimal point if num_digit is less than 0 (zero).
3. Example 1
The ROUNDDOWN function takes two arguments: the number to round and the number of digits to round to. Positive digits round to decimal places, 0 rounds to whole numbers, and negative digits round to tens, hundreds, thousands, etc.
Formula in cell D3:
- number = 11.3
- digits = 0
The function in cell D3 rounds 11.3 to the nearest whole number (0 decimal places) which is 11.
Formula in cell D4:
- number = 11.7
- digits = 0
The function in cell D4 rounds 11.7 down to the nearest whole number (0 decimal places) which is 11.
How to round a number down to one decimal places?
Formula in cell D5:
- number = 11.3
- digits = 1
The function in cell D5 rounds 11.3 down to 1 decimal places which is 11.3.
Formula in cell D6:
- number = 11.7
- digits = 1
The function in cell D6 rounds 11.7 down to 1 decimal places which is 11.7.
Formula in cell D7:
- number = 11.39
- digits = 1
The function in cell D7 rounds 11.39 to 1 decimal places which is 11.3.
Formula in cell D8:
- number = 11.32
- digits = 1
The function in cell D8 rounds 11.32 to 1 decimal places which is 11.3.
Formula in cell D9:
- number = 11.35
- digits = 1
The function in cell D9 rounds 11.35 to 1 decimal places which is 11.3.
How to round a number down to the nearest whole number?
Formula in cell D10:
- number = -1.2
- digits = 0
The function in cell D10 rounds -1.2 to the nearest whole number which is -1.
Formula in cell D11:
- number = -1.9
- digits = 0
The function in cell D11 rounds -1.9 to the nearest whole number which is -1.
How to round a number down to the nearest multiple of 10?
Formula in cell D12:
- number = 111
- digits = -1
The function in cell D12 rounds 111 down to -1 digits which rounds the value to tens. In this case: 110.
How to round a number down to the nearest multiple of 100?
Formula in cell D13:
- number = 111
- digits = -2
The function in cell D13 rounds 111 down to -2 digits meaning rounding the value to hundreds. In this case: 100.
How to round a number down to the nearest multiple of 1000?
Formula in cell D14:
- number = 111
- digits = -3
The function in cell D14 rounds 111 down to -3 digits meaning rounding the value to thousands. In this case: 0. 111 is closer to 0(zero) than 1000.
4. Example 2
What is the volume of a cone if the height (h) is 8 units and the radius (r) is 3 units? Round the number to two decimals.
Here is what we know:
- A cone has the following formula: volume = (π × r² × h)/3
- The height (h) is 8 units
- The radius (r) is 3 units.
Formula in cell C22:
The volume formula in cell C22 returns 75.39 square units. Here is how the formula works in simple terms:
- Calculate pi (π)
- Square the radius. 3² = 9
- Multiply pi by the radius squared by the height. π * 3² * 8 = 226.194671058465
- Divide the product by 3. 226.194671058465 / 3 = 75.398223686155
- Round the ratio down based on two decimals. 75.398223686155 becomes 75.39 square units.
Explaining formula in cell C22
Step 1 - Multiply pi by square radius by the height
The PI function returns the number pi (¶).
Function syntax: PI()
PI()*C19^2*C20
becomes
PI()*3^2*8
becomes
PI()*9*8
and returns 226.194671058465
Step 2 - Calculate the ratio
The division character lets you divide two numbers in an Excel formula.
226.194671058465 / 3 = 75.398223686155
Step 3 - Round the ration down to two decimals
ROUNDDOWN((PI()*C19^2*C20)/3,2)
becomes
ROUNDDOWN(75.398223686155,2)
and returns 75.39 square units.
'ROUNDDOWN' function examples
The picture above shows data presented in only one column (column B), this happens sometimes when you get an undesired […]
Functions in 'Math and trigonometry' category
The ROUNDDOWN function function is one of 62 functions in the 'Math and trigonometry' category.
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