These calculators cover the numbers that come up when you are judging an investment rather than simply tracking a savings balance: what a holding actually returned once time is accounted for, what a company pays out to shareholders and whether it can afford to keep doing so, what you are paying for each pound of earnings, and how a bond behaves when interest rates move. None of them tell you what to buy. What they do is convert the figures sitting in a set of accounts, a fund factsheet or a broker statement into something comparable across different holdings — which is exactly the part that is easy to get wrong doing it by hand.
Why the same numbers are calculated so many different ways
A single company can be described by a dozen different ratios, and the reason is that each one answers a different question. The price/earnings ratio asks what the market is paying for a pound of current profit. Price to book asks the same question against the accounting value of the net assets underneath the shares. Dividend yield and dividend cover ask whether the income is attractive and whether it is safe. Free cash flow yield asks the same "how much am I paying for this" question as the P/E ratio, but using cash actually generated rather than an accounting figure that includes non-cash charges like depreciation. None of these ratios is the single correct one — a serious look at any investment usually means checking several of them together, because each one can be flattering in isolation while the others tell a less generous story.
The mistake almost everyone makes with annualised returns
The most common error in this whole area is annualising a total return by simple division: an investment up 85% over seven years is not "12.1% a year". Because returns compound, the correct calculation — the compound annual growth rate, or CAGR — works out closer to 9.2% a year for that same example, and the gap between the two numbers widens the longer the holding period runs. It is the reason this section leads with an annualised return calculator: get that concept wrong and every comparison built on top of it, across every other calculator here, inherits the same error.
Bonds behave differently from shares
Several of these calculators — bond yield, yield to maturity, bond duration — deal with fixed income rather than equities, and the mathematics runs in a different direction. A bond's price and its yield move opposite to each other: when prevailing interest rates rise, existing bonds paying a lower fixed coupon become less attractive and their price falls until the yield an investor actually receives catches up with the market. Duration measures how sensitive a given bond's price is to that kind of rate move, expressed conveniently as a number of years. None of this is intuitive coming from equities, which is why bond mathematics tends to get skipped over in most general investing guidance despite bonds forming a substantial part of most diversified portfolios.
What these figures cannot tell you
Every calculator on this page works from figures you supply — a share price, a set of accounts, a coupon rate — and returns an honest calculation on those figures. What it cannot do is judge whether the figures themselves are reliable, whether a company's reported earnings reflect its real economic performance, or whether a bond issuer will actually make its payments. Ratios are a starting point for analysis, not a substitute for reading the underlying accounts, and past performance calculated here, like anywhere else, is not a guarantee of what comes next. Nothing on this page is personalised investment advice; it is arithmetic applied to numbers you choose to enter.
Comparing companies fairly
A ratio only becomes useful once it is compared against something — the same company a year ago, a direct competitor, or the sector it operates in. A price/earnings ratio of 22 is not intrinsically high or low; it is high relative to the broader market average, low relative to a fast-growing technology peer, and roughly average for many long-established consumer businesses. The calculators on this page will always give a correct answer to the specific question they are asked, but reading that answer against the right comparison group is where the actual judgement sits, and no formula can supply that judgement automatically.
Growth, value and income are different lenses
The ratios grouped here roughly sort into three traditions of looking at a business. Growth-oriented analysis leans on figures like the annualised return calculator, asking how fast a holding is compounding regardless of the price paid for it. Value-oriented analysis leans on price to earnings and price to book, asking what is being paid relative to current profit and net assets. Income-oriented analysis leans on dividend yield, payout ratio and dividend cover, asking how much cash a holding returns and how safely. None of the three approaches is objectively correct — professional investors build entire careers specialising in just one of them — and most of the disagreement you will see about whether a given share is "cheap" or "expensive" comes down to which of these three lenses is being applied rather than a disagreement about the underlying numbers.
Reading a set of company accounts
Every ratio on this page pulls from one of three financial statements: the income statement, which shows revenue and profit over a period; the balance sheet, which shows assets, liabilities and equity at a single point in time; and the cash flow statement, which shows cash actually moving in and out, independent of the accounting judgements that shape reported profit. A figure calculated from the income statement alone — earnings per share, for instance — can look strong even when the cash flow statement tells a more cautious story, which is exactly why this section includes free cash flow and free cash flow yield alongside the more familiar earnings-based ratios: reading both sides of the accounts together catches problems that either one, read alone, would miss.