I wanted to know when I would break even (including fees) on some bitcoins I bought on coinbase. So I built a brute force calculator.

coinbase_break_even_calculator.py

# -*- coding: utf-8 -*-

BANK_FEE = 0.15
COINBASE_PCT = 0.01


def calculate_sale_profit(coins, price, purchase_cost):
    value = round(coins * price, 2)
    fee = BANK_FEE + round(value * COINBASE_PCT)
    return (value - fee) - purchase_cost


def find_break_even(coins, purchase_cost):

    # Start at approx. purchase value
    current_value = round(purchase_cost / coins, 2)

    while True:
        profit = calculate_sale_profit(coins, current_value, purchase_cost)
        if profit >= 0:
            return current_value
        current_value += 0.01

if __name__ == '__main__':

    coins = float(raw_input('How many coins did you buy? '))
    cost = float(raw_input('How much was the (total) cost? '))

    print "Break even when 1 BTC == %0.02f" % find_break_even(coins, cost)

I love the idea of this. And I'm sorry to ask this... but where would you use this? Is this a potential script for a google sheet?