How to measure a currencies valuation or devaluation in relevance to itself
"It's very hard to measure the worth of an abstract concept like money, particularly over long periods of time. In the modern era we have things like the Consumer Price Index (CPI) in the United States, where the Bureau of Labor Statistics literally sends ""shoppers"" out to find prices of things and surveys people to find out what they buy. This results in a variety of ""indexes"" which variously get reported by media outlets as ""inflation"" (or ""deflation"" if the change in value goes the other way). There are also other measurements available like the MIT Billion Prices Project which attempt to make their own reading of the ""worth"" of currencies. Those kinds of things are about the only ways to measure a currency's change in ""value to itself"" because a currency is basically only worth what one can buy with it. While it isn't ""all the world's currencies combined"", there is a concept of the International Monetary Fund's ""Special Drawing Rights (SDR)"", which is a basket of five currencies used by world central banks to help ""back"" each other's currencies, and is (very) occasionally used as a unit of currency for international contracts. One might be able to compare the price of one currency to that of the SDR, or even to any other weighted average of world currencies that one wanted, but I don't think it's done nearly as often as comparing currencies to the basket of goods one can buy to find ""inflation"". Even though one might think what would be important to measure would be overall Money Supply Inflation, much more often people care more about measuring Price Inflation. (Occasionally people worry about Wage Inflation, but generally that's considered a result of high Price Inflation.) In order to try to keep this on topic as a ""personal finance"" thing rather than an ""economics"" thing, I guess the question is: Why do you want to know? If you have some assets in a particular currency, you probably care most about what you'll be able to buy with them in the future when you want or need to spend them. In that sense, it's inflation that you're likely caring about the most. If you're trying to figure out which currency to keep your assets in, it largely depends on what currency your future expenses are likely to be in, though I can imagine that one might want to move out of a particular currency if there's a lot of political instability that you're expecting to lead to high inflation in a currency for a time." The measure of change of value of a currency in relation to itself is inflation (or deflation). As the value of a currency declines, commodities, priced in that currency, will rise. The two best commodities to see a change in would be oil and gold.
No. The long-term valuation of currencies has to do with Purchasing Power Parity.  The long-term valuation of stocks has to do with revenues, expenses, market sizes, growth rates, and interest rates. In the short term, currency and stock prices change for many reasons, including interest rate changes, demand for goods and services, asset price changes, political fears, and momentum investing.  In any given time window, a currency or stock might be: The Relative Strength Index tries to say whether a currency or stock has recently been rising or falling; it does not inherently say anything about whether the current value is high or low. Arguably, the only reason the US can print dollar without massive repercussions on devaluing it is because of it is the world's reserve currency, backed by oil. This has allowed to US to build the world's biggest and most powerful army because they can easily borrow money to fund it. Everyone needs oil for their economy, therefore everyone needs dollars... They wont let it collapse, they will devalue it over time to some effect via bailouts and borrowing.  Invest in commodities so your cash retains its value, physical gold is always strong.  Other currencies are an option but this is more of a gamble. A good fundamental test book, besides Damodaran already mentioned in the comments, is: Valuation - Measuring and Managing the Value of Companies by Tim Koller, Marc Goedhart and David Wessels. It gives a very good breakdown of the DCF method for Valuation. "Currencies that are pegged or fixed require that foreign currencies are held by the central issuer at a proportional amount. This is analogous to having a portfolio of currencies that the central bank issues shares from - in the form of its own currency. We will continue with this analogy, if the central bank says these ""shares"" are worth $1, but the underlying components of the portfolio are worth $0.80 and decreasing, then it is expensive for the central bank to maintain its peg, and eventually they will have to disregard the peg as people start questioning the central bank's solvency. (People will know the $1 they hold is not really worth what the central bank says it is, because of the price changes people experience in buying goods and services, especially when it comes to imports. Shadow economies will also trade using a currency more reflective of labor, which happens no matter what the government's punishments are for doing so). Swiss National Bank (central bank) did this in early 2015, as it experienced volatility in the Euro which it had previously been trying to keep it's currency pegged to. It became too expensive for it to keep this peg on its own. The central bank can devalue its currency by adjusting the proportions of the reserve, such as selling a lot of foreign currency X, buying more of currency Y. They can and do take losses doing this. (Swiss National Bank is maintaining a large loss) They can also flood their economy with more of their currency, diluting the value of each individual 1 dollar equivalent. This is done by issuing bonds or monetizing goods and services from the private sector in exchange for bonds. People colloquially call this ""printing money"" but it is a misnomer in this day and age where printers are not relevant tools. The good and service goes onto the central bank's balance book, and the company/entity that provided the service now has a bond on its book which can be immediately sold to someone else for cash (another reading is that the bond is as good as cash). The bond didn't previously exist until the central bank said it did, and central banks can infinitely exchange goods and services for bonds. Bond monetization (also called Quantitative Easing) is practiced by the Federal Reserve in the United States, Bank of Japan, European Central Bank and now the Central Bank of the Republic of China" "Once a currency loses value, it never regains it. Period. Granted there have been short term periods of deflation, as well as periods where, due to relative value fluctuation, a currency may temporarily gain value against the U.S. dollar (or Euro, Franc, whatever) but the prospect of a currency that's lost 99.99% of its value will reclaim any of that value is an impossibility. Currency is paper. It's not stock. It's not a hard commodity. It has no intrinsic value, and no government in history has ever been motivated to ""re-value"" its currency. Mind you, there have been plenty of ""reverse splits"" where a government will knock off the extraneous zeroes to make handling units of the currency more practical." "First of all, setting some basics: What is a sound way to measure the risk of each investment in order to compare them with each other ? There is no single way that can be used across all asset classes / risks. Generally speaking, you want to perform both a quantitative and qualitative assessment of risks that you identify.  Quantitative risk assessment may involve historical data and/or parametric or non-parametric models. Using historical data is often simple but may be hard in cases where the amount of data you have on a given event is low (e.g. risk of bust by investing in a cryptocurrency). Parametric and non-parametric risk quantification models exist (e.g. Value at Risk (VaR), Expected Shortfall (ES), etc) and abound but a lot of them are more complicated than necessary for an individual's requirements. Qualitative risk assessment is ""simply"" assessing the likelihood and severity of risks by using intuition, expert judgment (where that applies), etc. One may consult with outside parties (e.g. lawyers, accountants, bankers, etc) where their advisory may help highlighting some risks or understanding them better. To ease comparing investment opportunities, you may want to perform a risk assessment on categories of risks (e.g. investing in the stock market vs bond market). To compare between those categories, one should look at the whole picture (quantitative and qualitative) with their risk appetite in mind. Of course, after taking those macro decisions, you would need to further assess risks on more micro decisions (e.g. Microsoft or Google ?). You would then most likely end up with better comparatives as you would be comparing items similar in nature. Should I always consider the worst case scenario ? Because when I do that, I always can lose everything. Generally speaking, you want to consider everything so that you can perform a risk assessment and decide on your risk mitigating strategy (see Q4). By assessing the likelihood and severity of risks you may find that even in cases where you are comparatively as worse-off (e.g. in case of complete bust), the likelihood may differ. For example, keeping gold in a personal stash at home vs your employer going bankrupt if you are working for a large firm. Do note that you want to compare risks (both likelihood and severity) after any risk mitigation strategy you may want to put in place (e.g. maybe putting your gold in a safety box in a secure bank would make the likelihood of losing your gold essentially null). Is there a way to estimate the probability of such events, better than intuition ? Estimating probability or likelihood is largely dependent on data on hand and your capacity to model events. For most practical purposes of an individual, modelling would be way off in terms of reward-benefits. You may therefore want to simply research on past events and assign them a 1-5 (1 being very low, 5 being very high) risk rating based on your assessment of the likelihood. For example, you may assign a 1 on your employer going bankrupt and a 2 or 3 on being burglarized. This is only slightly better than intuition but has the merit of being based on data (e.g. frequency of burglary in your neighborhood). Should I only consider more probable outcomes and have a plan for them if they occur? This depends largely on your risk appetite. The more risk averse you are, the more thorough you will want to be in identifying, tracking and mitigating risks. For the risks that you have identified as relevant, or of concern, you may opt to establish a risk mitigating strategy, which is conventionally one of accepting, sharing (by taking insurance, for example), avoiding and reducing. It may not be possible to share or reduce some risks, especially for individuals, and so often the response will be either to accept or avoid the given risks by opting in or out on an opportunity." At any instant, three currencies will have exchange rates so if I know the rate between A and B, and B to C, the A to C rate is easily calculated. You need X pounds, so at that moment, you are subject to the exchange rate right then. It's not a deal or bargain, although it may look better in hindsight if the currencies move after some time has passed. But if a currency is going to depreciate, and you have the foresight to know such things, you'd already be wealthy and not visiting here.