Hi all,
I have been beating my brain to death trying to remember how to do this… I need to account for a fee I am being charged. Example. Amazon chargers 15% fee on products sold. On my website a product costs $100.00 So, how much do I need to mark the price up to off set that fee? All I want to is end up back at my original $100 so it’s not a 15% mark up because the fee on $115 sale is $17.25 leaving only $97.75.
If someone can tell me how to do this I would really appreciate it 
Since you want your price after a 15% fee to be $100, then that means that $100 is 85% of the base price. Just do $100 / 0.85 = ~$117.65 to work backwards and find the base price.
Just to clarify the above,
New Price = Price / (1- discount%)
Edit: (discount% is in 0 to 1 format)
Serlite, THANK YOU!!!
I wondered how much amazon charges. Does that include fees on payments also, or is that in addition to the 15%?
ebay charges 10, then there is ~3 more for paypal. Not much less than 15% if you don’t have to pay for money laundering extra.
Its 15% on the item value. On most items, there are some its lees, and when you get up to items worth like 10K you get a break and on a few other things. No 3% PP fee though as amazon makes a direct deposit into your bank account. Not sure if that is once a month or if it will be on each sale etc as I’ve not listed yet. In addition you have to pay $40 per month business member fee. Alternatively an individual selling only a few things can pay $1 per item sold.
thanks for the response. 
So, what are you going to be selling on Amazon? 
likely nothing, as the price is too high. I have bought significantly discounted lights and resold them on ebay, its a good way to buy several and keep one for essentially free. I am still trying to sell my last Olight H1, but no one is biting. That one is free, so I may just end up giving it away or keeping it for myself, we will see.
The same things I sell in my shop for 15% less money