Rounding a number to the nearest 5 or 10 or X

Question

It's simple math. Given a number X and a rounding factor N, the formula would be:

round(X / N)*N

Integrated Answer

X = 1234 'number to round
N = 5    'rounding factor
round(X/N)*N   'result is 1235

For floating point to integer, 1234.564 to 1235, (this is VB specific, most other languages simply truncate) do:

int(1234.564)   'result is 1235

Beware: VB uses Bankers Rounding, to the nearest even number, which can be surprising if you're not aware of it:

msgbox round(1.5) 'result to 2
msgbox round(2.5) 'yes, result to 2 too

Thank you everyone.

To round to the nearest X (without being VBA specific)

N = X * int(N / X + 0.5)

Where int(...) returns the next lowest whole number.

If your available rounding function already rounds to the nearest whole number then omit the addition of 0.5

In VB, math.round has additional arguments to specify number of decimal places and rounding method. Math.Round(10.665, 2, MidpointRounding.AwayFromZero) will return 10.67 . If the number is a decimal or single data type, math.round returns a decimal data type. If it is double, it returns double data type. That might be important if option strict is on.

The result of (10.665).ToString("n2") rounds away from zero to give "10.67". without additional arguments math.round returns 10.66, which could lead to unwanted discrepancies.

'Example: Round 499 to nearest 5. You would use the ROUND() FUNCTION.

a = inputbox("number to be rounded")
 b = inputbox("Round to nearest _______ ")


  strc = Round(A/B)
  strd = strc*B


 msgbox( a & ",  Rounded to the nearest " & b & ", is" & vbnewline & strd)

For a strict Visual Basic approach, you can convert the floating-point value to an integer to round to said integer. VB is one of the rare languages that rounds on type conversion (most others simply truncate.)

Multiples of 5 or x can be done simply by dividing before and multiplying after the round.

If you want to round and keep decimal places, Math.round(n, d) would work.

Here is our solution:

Public Enum RoundingDirection
    Nearest
    Up
    Down
End Enum

Public Shared Function GetRoundedNumber(ByVal number As Decimal, ByVal multiplier As Decimal, ByVal direction As RoundingDirection) As Decimal
    Dim nearestValue As Decimal = (CInt(number / multiplier) * multiplier)
    Select Case direction
        Case RoundingDirection.Nearest
            Return nearestValue
        Case RoundingDirection.Up
            If nearestValue >= number Then
                Return nearestValue
            Else
                Return nearestValue + multiplier
            End If
        Case RoundingDirection.Down
            If nearestValue <= number Then
                Return nearestValue
            Else
                Return nearestValue - multiplier
            End If
    End Select
End Function

Usage:

dim decTotal as Decimal = GetRoundedNumber(CDec(499), CDec(0.05), RoundingDirection.Up)