what is the formula used for the reverse square calculator

[confused]

What is the formula to calculate how much fee to charge so that one can net a particular $ amount, specifically when entering a credit card number manually. I realise the manual swippng fee formula is 3.5% + $0.15 but for example to net $100 on a sale you would enter ($100 * 1.035) + $0.15 = $103.65, however this does not net $100. The reverse Square calculator instructs you to enter $103.78 to net $100 which works. So, the difference (error?) on a $100 manual transaction is $0.13, I can not determine where the additional 13 cents comes from.     

[VanKalkerFarms]

It is because you are taking 3.5% of the additional $3.65 also, so you have to take into account for that too. 

$3.50 for CC charge

$.15 for swipe on manual

$.13 for the CC charge on the $3.50

so take your total you want to net. Times it by 1.0363 and add $.15. Your net after fees should be what you want. 

Example

If manually entering a $100 sale

use 3.63% + $.15

100*1.0363=103.63

103.63+.15=103.78

charge 103.78 and your fee from square will be $3.63 + $.15 netting $100

Example

If swiping the card for a $100 sale

use 2.83%

$100*1.0283=$102.83

Charge $102.83 and your fee from square will be $2.83 netting $100

[alohaboy]

This topic is old, but here's the formula:

((((OT*SQ%)+SQ$)+OT)*SQ%)+SQ$ = NT

OT = Original Total

SQ% = Square Percentage Charge

SQ$ = Square Per Transaction $ Fee

NT = New Total (the amount to charge the customer)

For a Square transaction fee of 2.9% + $0.30:

((((OT*0.029)+0.3)+OT)*0.029)+0.3 = NT