Function guides · Math
ROUNDDOWN function
Rounds a number toward zero to a set number of digits.
Syntax
=ROUNDDOWN(number, num_digits)
| Argument | What it is |
|---|---|
number | The number to round. |
num_digits | Decimal places to keep. 0 for a whole number, negative for tens, hundreds and so on. |
What ROUNDDOWN does
ROUNDDOWN cuts a number back toward zero. Whatever comes after the digit you keep is thrown away, even if it is .99.
Where ROUNDUP guards against falling short, ROUNDDOWN counts only what is complete. A project that has run 4.9 years has completed 4. A pallet holding 47.9 cases holds 47 full ones.
Its digit argument follows the same rule as ROUND: positive for decimals, zero for whole numbers, negative for tens and hundreds.
TRUNC is the sibling that most people meet next. It also cuts digits off toward zero and takes the same arguments, so ROUNDDOWN and TRUNC agree on every input. The one behavioral difference people notice is on negative numbers compared with INT, which rounds down instead.
When a rule says “round down to the nearest 5” or “to the nearest quarter hour”, digits will not do. FLOOR and MROUND work on multiples rather than decimal places. Use ROUNDDOWN when the rule is about decimal places or whole units, and FLOOR when the rule names a step size.
A small example makes the choice clear. If a tenant has lived somewhere 4 years and 11 months, ROUND on the decimal 4.92 says 5. Excel’s DATEDIF says 4. The rule “complete years only” is ROUNDDOWN, and tests that mention complete, full or elapsed are looking for it.
ROUNDDOWN examples
1. Full cases only
| A | B | C | |
|---|---|---|---|
| 1 | Item | Cases | |
| 2 | Paper | 47.9 | 47 |
A shipment of 47.9 cases includes only 47 complete ones. ROUNDDOWN drops the fraction, however large it is.
2. Truncate to cents
| A | B | C | |
|---|---|---|---|
| 1 | Item | Price | |
| 2 | Filter | 7.899 | 7.89 |
A computed price of 7.899 becomes 7.89, not 7.90. This is how some systems cut off fractions of a cent instead of rounding them.
3. Toward zero for negatives
| A | B | |
|---|---|---|
| 1 | Change | |
| 2 | -3.8 | -3 |
ROUNDDOWN goes toward zero, so -3.8 becomes -3. INT would return -4, since INT always goes to the next lower integer.
Common ROUNDDOWN mistakes
- Assuming it matches INT on negatives. ROUNDDOWN(-3.8,0) is -3 and INT(-3.8) is -4. They agree only for positive numbers.
- Using ROUND where truncation is required. A rule like "only count full years" needs ROUNDDOWN or INT. ROUND would count 4.7 years as 5.
- Negative digits misread. ROUNDDOWN(1849,-2) is 1800. Negative digits move the cut to the left of the decimal point.
ROUNDDOWN on Excel job tests
Look for "complete", "full" and "whole units only": complete years of service, full boxes, whole hours worked. The prompt rarely says round, and the next column is often the remainder, which is MOD.
For positive numbers ROUNDDOWN and INT agree. If the data has refunds or adjustments, a negative row will show the difference, so read the sign before choosing.
To cut a price to cents without rounding, ROUNDDOWN with 2 digits does it. Make sure the cell holds the cut value and not just a number format that hides the extra digits.
Related functions
ROUNDDOWN questions
- What is the difference between ROUNDDOWN and INT?
- Both drop the fraction of a positive number. For negatives, ROUNDDOWN moves toward zero and INT moves to the next lower integer.
- How do I round down to the nearest 10?
- Use -1:
=ROUNDDOWN(B2,-1). For multiples such as 5, use FLOOR. - Does ROUNDDOWN ever round up?
- No. It always moves toward zero.
- How do I get only the whole part of a number?
- For positive numbers
=ROUNDDOWN(A2,0)or=INT(A2)both work.
Practice ROUNDDOWN
No lesson is built around ROUNDDOWN yet. The closest thing to practice is a free 5-item sample test, which uses the same kind of formulas in a working grid. The Everyday Excel track shows what is published.
Try a 5-item Excel test sample