A calculator that answers in a sentence

InvestingLite exists because the good investing calculators are hard to read and the readable ones are surrounded by things trying to sell you something. Both problems have the same root: most of these tools are built to capture an email address, and the arithmetic is the bait.

This site has nothing to sell you. There is no account, no newsletter, no affiliate links to brokers and no analytics. The calculators run entirely in your browser — your numbers never leave the page except into your own address bar, so that a scenario can be bookmarked or sent to someone. How it is funded is set out below.

The three rules it is built on

Answer in words, not just digits. A number without an interpretation makes you do the work of deciding whether it is good news. Every result here comes with a sentence explaining it, generated from the same figures — so the words can never drift away from the chart above them.

Never show one number where three are honest. A single projected figure reads as a promise. Every tool prices the same plan at a cautious, middle and optimistic return, side by side. The width of that gap is usually the most useful thing on the page.

Never give advice. This is a maths site. It will not tell you what to buy, what return to expect, or whether your plan is sensible — not out of caution, but because a website does not know your circumstances and anything it said would be a guess wearing a confident tone. The disclaimer says this more formally.

What it gets right that others often do not

• An annual rate is converted to a monthly one properly. Type 7% and your money is 7% larger after twelve months — not the 7.23% that dividing by twelve quietly produces.
• Contributions land at the end of the month, as a standing order does, rather than being credited a month early.
• Withdrawals in the drawdown tool rise with inflation, because an income held flat for thirty years is an income that shrinks.
• Fees are modelled as a deduction from the return on the whole balance, which is how they are actually charged.

The full method is written up here, including what the calculators deliberately ignore.

How it is paid for

The site is funded by advertising, served by Google AdSense. That pays for the domain and hosting and keeps every calculator free with no account and no email capture. Some readers also send a small amount toward the running costs, which buys them nothing beyond the calculators everyone else already gets free. What it does not buy is influence over the content: no advertiser sees a page before it goes up, nothing on this site is ranked or recommended in exchange for payment, and there are no affiliate links to brokers or platforms. The calculators are deliberately built to have no opinion about what you should buy, which makes them a poor vehicle for selling anything — that is a feature, and it is not for sale.

Corrections

If a number here is wrong, that is a bug and worth reporting — the maths is covered by a test suite precisely so that errors are findable. Write to hello@investinglite.com.