Derive Gross Pay plus Payroll Taxes from a Gross Amount

I'm trying to write an Excel formula that will take a gross starting number (GSN) and then will compute gross salary, FICA, and Medicare that will add up to equal that amount.

FICA is 6.2% of gross salary, but only on the first $118,500 of salary
Medicare is 1.45% of gross salary, with no top limit.

This would be easy if there wasn't that $118,500 threshold for FICA

For example,

Gross Starting Number = 107,650

would give you:
Gross salary = 100,000
FICA = 6,200
Medicare = 1,450

I can only tell you these numbers by starting with the gross salary, computing the payroll taxes, and then adding them all up to arrive at the Gross Starting Number, but I need a formula that will give me the same numbers starting with the GSN. Can anyone see a way to do this? Thanks for any help.

Thanks for the effort, but this isn't working form me. Where GSN = 107,650

Gross salary = 99,415
FICA = 6,164
Medicare = 1,442
Total = 107,020

There is an difference of 630 from GSN.

See attached:

Calculated GS:

in G2

=IF($G2<=118000*(1+$A2+$B2),$G2/(1+$A2+$B2),($G2-118000*$A2)/(1+$B2))

A2= FICA %

B2 = Medicare %

G2=Calculated GSN

Interim calculations

in E2

=MIN(D5,118000)*A5

in F2

=D2*B2

in G2

=SUM(D2:F2)

Exactly. That was my question.

Someone on another Excel forum suggested using the Goal Seek function, which I had never heard of. It works for this, but it's not a formula. If you want to make it work automatically in a spreadsheet, you have to delve into VBA programming.

John Topley, this isn't what I'm looking for. You're starting with the Gross Salary to compute GSN. I need to start with the GSN to calculate the Gross Salary. Thanks for the effort.

Okay. That's not clear from what you've posted. You had a formula in the GSN column, which doesn't make it seem likes it's where data should be entered.

I've changed the spreadsheet to make it do what I think you meant for it to do and entered various GSN values in column G. I also changed column D so it will pull it's value form column I

Doing that, the columns add up correctly, as shown in column K, but the FICA isn't maxing out at $118k. It keeps going up to $127,026.98. I've attached the spreadsheet with my changes on the first tabl

Thanks for your help.

FICA isn't maxing out at $118k

unless I misunderstood the FICA reaches a maximum at $118000 salary which equates to $7136. Any figure > $118000 has FICA of 7136 (column E).

Ah, you're right. I was looking at the wrong column. Thanks!