Figuring out how much I must send given deductions

trav1085

New member
Joined
Oct 3, 2018
Messages
1
I'm working on a spreadsheet with some currency conversion related formulas. One of them is calculating the total amount transferred after fees are applied. The units are in Bitcoin.

Total sent = (Sum total - 0.00025) - (Sum total * 0.5%)


So, if I am sending 0.123 bitcoin then after fees the total sent is 0.122135

That's the easy part, but I want to calculate it the other way around, that is,

I wish to add a way to calculate how much I must send to compensate for deducted fees.

I thought about it for a bit and played around with some things and came up with this formula, which always gets very close and with rounding would be considered correct.

Sum total = (Total + 0.00025) + ((Total + 0.00025) * 0.5%)

So, if we wish to send 0.122135 compensating for fees then we must send a total of 0.122996925.

Where is the 0.000625 gone? Can I tweak my formula so it is 100% accurate?
 
I'm working on a spreadsheet with some currency conversion related formulas. One of them is calculating the total amount transferred after fees are applied. The units are in Bitcoin.

Total sent = (Sum total - 0.00025) - (Sum total * 0.5%)


So, if I am sending 0.123 bitcoin then after fees the total sent is 0.122135

That's the easy part, but I want to calculate it the other way around, that is,

I wish to add a way to calculate how much I must send to compensate for deducted fees.

I thought about it for a bit and played around with some things and came up with this formula, which always gets very close and with rounding would be considered correct.

Sum total = (Total + 0.00025) + ((Total + 0.00025) * 0.5%)

So, if we wish to send 0.122135 compensating for fees then we must send a total of 0.122996925.

Where is the 0.000625 gone? Can I tweak my formula so it is 100% accurate?
Try using what you learned in high-school algebra. (I'll use "Ts" for "Total sent" and "St" for "Sum total". I'll also write "0.5%" as "0.005".)

. . . . .Ts = (St - 0.00025) - (0.005*St)

. . . . .Ts = 1*St - 0.00025 - 0.005*St

. . . . .Ts = 0.995*St - 0.00025

Then add the constant term to each side, to move it to the left-hand side:

. . . . .Ts + 0.00025 = 0.995*St

Then divide through to complete the isolation of St. ;)
 
Total sent = (Sum total - 0.00025) - (Sum total * 0.5%)

So, if I am sending 0.123 bitcoin then after fees the total sent is 0.122135

That's the easy part, but I want to calculate it the other way around, that is,
I wish to add a way to calculate how much I must send to compensate for deducted fees.
Sorry, but your wording is quite confusing; changing it to:

Net sent = (amount sent - .00025 - amount sent * .005)
Lose less hair by using variables:

n = Net sent = .123
u = .00025
v = .005
a = amount sent = ?

n = a - u - a*v
n = a*(1 - v) - u
a*(1 - v) = n + u

Divide through to obtain the general case formula

So a = (.123 + .00025) / (1 - .005) = ~ (approximately how much?)

So, by sending [that much], you end up with your 0.123 net.
 
Last edited by a moderator:
Top