Calculate percentage saved between two numbers?
MathFormulaMath Problem Overview
I have two numbers, the first, is the original price, the second, is the discounted price.
I need to work out what percentage a user saves if they purchase at the second price.
example
25, 10 = 60%
365, 165 = 55%
What I dont know is the formula to calculate this.
Math Solutions
Solution 1 - Math
I know this is fairly old but I figured this was as good as any to put this. I found a post from yahoo with a good explanation:
Let's say you have two numbers, 40 and 30.
30/40*100 = 75.
So 30 is 75% of 40.
40/30*100 = 133.
So 40 is 133% of 30.
The percentage increase from 30 to 40 is:
(40-30)/30 * 100 = 33%
The percentage decrease from 40 to 30 is:
(40-30)/40 * 100 = 25%.
These calculations hold true whatever your two numbers.
Solution 2 - Math
((list price - actual price) / (list price)) * 100%
For example:
((25 - 10) / 25) * 100% = 60%
Solution 3 - Math
I see that this is a very old question, but this is how I calculate the percentage difference between 2 numbers:
(1 - (oldNumber / newNumber)) * 100
So, the percentage difference from 30 to 40 is:
(1 - (30/40)) * 100 = +25% (meaning, increase by 25%)
The percentage difference from 40 to 30 is:
(1 - (40/30)) * 100 = -33.33% (meaning, decrease by 33%)
In php, I use a function like this:
function calculatePercentage($oldFigure, $newFigure) {
if (($oldFigure != 0) && ($newFigure != 0)) {
$percentChange = (1 - $oldFigure / $newFigure) * 100;
}
else {
$percentChange = null;
}
return $percentChange;
}
Solution 4 - Math
The formula would be (original - discounted)/original. i.e. (365-165)/365 = 0.5479...
Solution 5 - Math
function calculatePercentage($oldFigure, $newFigure)
{
$percentChange = (($oldFigure - $newFigure) / $oldFigure) * 100;
return round(abs($percentChange));
}
Solution 6 - Math
100% - discounted price / full price
Solution 7 - Math
I have done the same percentage calculator for one of my app where we need to show the percentage saved if you choose a "Yearly Plan" over the "Monthly Plan". It helps you to save a specific amount of money in the given period. I have used it for the subscriptions.
> Monthly paid for a year - 2028 > Yearly paid one time - 1699 > > 1699 is a 16.22% decrease of 2028. > > Formula: Percentage of decrease = |2028 - 1699|/2028 = 329/2028 = 0.1622 > = 16.22%
Code:
func calculatePercentage(monthly: Double, yearly: Double) -> Double {
let totalMonthlyInYear = monthly * 12
let result = ((totalMonthlyInYear-yearly)/totalMonthlyInYear)*100
print("percentage is -",result)
return result.rounded(toPlaces: 0)
}
Usage:
let savingsPercentage = self.calculatePercentage(monthly: Double( monthlyProduct.price), yearly: Double(annualProduct.price))
self.btnPlanDiscount.setTitle("Save \(Int(savingsPercentage))%",for: .normal)
The extension usage for rounding up the percentage over the Double:
extension Double {
/// Rounds the double to decimal places value
func rounded(toPlaces places:Int) -> Double {
let divisor = pow(10.0, Double(places))
return (self * divisor).rounded() / divisor
}
}
I have attached the image for understanding the same:
Solution 8 - Math
If total no is: 200 and getting 50 number
then take percentage of 50 in 200 is:
(50/200)*100 = 25%
Solution 9 - Math
This is function with inverted option
It will return:
- 'change' - string that you can use for css class in your template
- 'result' - plain result
- 'formatted' - formatted result
function getPercentageChange( $oldNumber , $newNumber , $format = true , $invert = false ){
$value = $newNumber - $oldNumber;
$change = '';
$sign = '';
$result = 0.00;
if ( $invert ) {
if ( $value > 0 ) {
// going UP
$change = 'up';
$sign = '+';
if ( $oldNumber > 0 ) {
$result = ($newNumber / $oldNumber) * 100;
} else {
$result = 100.00;
}
}elseif ( $value < 0 ) {
// going DOWN
$change = 'down';
//$value = abs($value);
$result = ($oldNumber / $newNumber) * 100;
$result = abs($result);
$sign = '-';
}else {
// no changes
}
}else{
if ( $newNumber > $oldNumber ) {
// increase
$change = 'up';
if ( $oldNumber > 0 ) {
$result = ( ( $newNumber / $oldNumber ) - 1 )* 100;
}else{
$result = 100.00;
}
$sign = '+';
}elseif ( $oldNumber > $newNumber ) {
// decrease
$change = 'down';
if ( $oldNumber > 0 ) {
$result = ( ( $newNumber / $oldNumber ) - 1 )* 100;
} else {
$result = 100.00;
}
$sign = '-';
}else{
// no change
}
$result = abs($result);
}
$result_formatted = number_format($result, 2);
if ( $invert ) {
if ( $change == 'up' ) {
$change = 'down';
}elseif ( $change == 'down' ) {
$change = 'up';
}else{
//
}
if ( $sign == '+' ) {
$sign = '-';
}elseif ( $sign == '-' ) {
$sign = '+';
}else{
//
}
}
if ( $format ) {
$formatted = '<span class="going '.$change.'">'.$sign.''.$result_formatted.' %</span>';
} else{
$formatted = $result_formatted;
}
return array( 'change' => $change , 'result' => $result , 'formatted' => $formatted );
}
Solution 10 - Math
I think this covers this formula sufficiently,
((curr value - base value) / (curr value)) * 100%
Basically we just (in programming):
- perform the calculation if both numbers are not 0.
- If curr value is 0 then we return -100 % difference from the base,
- if both are 0 then return 0 (we can't divide by 0)
Powershell example:
Strip any non numeric from vars and perform calculation
Function Get-PercentageSaved {
#((curr value - base value) / (curr value)) * 100%
param(
[Parameter(Mandatory = $false)][string]$CurrVal = $null,
[Parameter(Mandatory = $false)][string]$BaseVal = $null
)
$Result = $null
Try {
$CurrVal = [float]($CurrVal -replace '[^0-9.]', '')
$BaseVal = [float]($BaseVal -replace '[^0-9.]', '')
if (-Not($null -eq $CurrVal) -And (-Not($null -eq $BaseVal))) {
if ($CurrVal -eq 0) {
If ($BaseVal -eq 0) {
$Result = 0
} Else {
$Result = -100
}
}
else {
$Result = [math]::Round([float]((($CurrVal - $BaseVal) / $CurrVal) * 100),2)
}
}
}
Catch {}
Return [float]$Result
}