Bitcoin Forum

I alwasy wandered what a formula is to hand convert any amount of BTC to USD is based on the variable exchange rate.. what Is it anyhow?

Demand and Supply.
Search it up.

no I mean as in if I have 0.08 BTC in my wallet (Which I do) and 1 BTC is worth $10.50, how much is 0.08 BTC? How did you get the answer?

Use a calculator to multiply the price times the amount. So your 0.08 BTC at $10.50 is equivalent to $0.84.

Not that we need it, but I checked to see if Wolfram-Alpha understood bitcoins yet. It does not.

Physics class taught me how to do nearly all unit conversions.  First, start with the ratio of one unit to another and represent it as a fraction, with the desired unit on top:


Then multiply that fraction by the value you currently know over a unitless 1:


The units that you start with will cancel out, since one is on top and the other on bottom.  You'll be left with just the unit type you want.


Now actually do the math, and you have your value:

 just do what rubic said

X USD = e^{t} * 1 BTC

Where t=0 is the moment one BTC was worth one USD.

Being new to Bittrex, I made some purchases without writing down the amount in US dollars, assuming it would be saved in the order history. But, everything is in BTC conversions and not in US dollars.

Is there a way to determine how much US dollars you purchased a particular coin at? For instance, if I bought OMG 3 weeks ago, how much did I pay for it in US dollars based on today's current BTC value? If this is impossible, wouldn't it be nice to have the amount of US dollars saved in some format so you can see how much your coin is currently worth in US dollars?

Actually there is no formula. The whole concept is of demand and supply. Suppose buyers agree to give X price and sellers agree to sell at Y price in particular market. So bitcoin price is actually a consensus price between  X and Y where both buyer and seller agree to trade.
So this consensus price differs in different market hence we have variable prices across globe.

I disagree to this statement. There will always be a formula to conversions. The digits will not just pop up and there we go, the price is this: $x. If you are telling that the price is to decided by the agreement of both seller and buyer then you are just saying that someone is controlling the price, thus Bitcoin is centralized. It seems that your logic has many flaws.

Go to Preev.com you may find what you are looking for. 8)

How could you say if buyers and sellers decide their prices then its centralized? Centralization means a single body deciding price and all buyers and sellers follow that. But when both have liberty setting their own prices, it fulfills decentralized criteria on its own.
And believe me there is no formula of conversions. The prices are just mean of different buy and sell orders where both buyers and sellers agree to trade.

4
down vote
I will explain how to calculate the value of some amount of bitcoins in terms of USD, but obviously the USD can be replaced by any other currency, and the corresponding exchange rate.

There are three figures involved in this calculation:

The value in USD.
The exchange rate, which gives you the relation of USD to BTC.
The amount of bitcoins.
If you look at the units of the figures, you can figure out the following formula:

value in USD = exchange rate * amount of bitcoins

Or expressed in the units of the terms:

[USD] = [USD/BTC] * BTC

As you can see, if you multiply the exchange rate [USD/BTC] with the amount of bitcoins BTC, the units of the right side will be reduced to [USD], which is what we are looking for.

Example:
We have 0.005 BTC and the exchange rate is 200 USD/BTC.

exchange rate * amount of bitcoins = 200 USD/BTC * 0.005 BTC = 200 USD * 0.005 = 1 USD

You can also turn the equation around to calculate any of the other terms:

To calculate the exchange rate, you take the amount of USD you paid, and divide by the amount of bitcoins you received.

exchange rate = 'value in USD' / 'number of bitcoins'

To calculate the number of bitcoins you might buy with a given amount of USD at a specific exchange rate, you divide the amount of USD by the exchange rate:

number of bitcoins = 'value in USD' / 'exchange rate'

every exchange site calculate Demand and supply and then detect price. this is why some exchange site give you high price.
 others give you average price.

I think there is no definite formula on this one. Since all exchanges has its different rate. What you can check is which exchange usually dictates the market value and others will follow. For me, I use BITSTAMP(this is not a plug).

Go to Preev.com you will probably find what you have been looking for.

This might help.
https://99bitcoins.com/satoshi-usd-converter

I woner where are this guys who wrote on this topic in 2011 :)
First version: Living on their private island.
Second version: Crying that not invested in Bitcoin in those days.