Horalis Dividends: what dividends pay over the years

• Code: projects/dividends/src/calc.ts (the calculation), src/view.ts (the sentence, the chart and the table), src/app.ts (the form and the link).
• Data: none. The person types everything; the example the page opens with is round numbers, not an estimate.
• Tests: projects/dividends/test/calc.test.ts and site.test.ts.

Question it answers

"What will my dividends pay over the years?": with the page's example, "In 20 years you will receive ≈ €3,598 a year (≈ €300 a month), after tax; in today's money, ≈ €2,421". Each figure with ≈ and in whole units of the currency.

Formula in plain words

Month by month. A share starts at a price of 1 and pays each year the dividend yield the person types; so what is invested is shares.

1. The shares held are paid a twelfth of the year's dividend.
2. The tax the person types comes off.
3. What is paid is kept as cash, or buys more shares at that month's price when reinvested.
4. The month's amount buys shares at the end of the month.
5. The dividend grows a month: (1 + yearly growth)^(1/12). So does the price, as the dividend does or at its own pace (see assumptions).

Exact, for each month: paid = shares × dividend ÷ 12 × (1 − tax); shares += paid ÷ price (if reinvested) + amount ÷ price; dividend × (1 + g)^(1/12); price × (1 + p)^(1/12). What it is worth at the end is shares × price. In today's money, what the last year paid ÷ (1 + inflation)^years.

Assumptions

• The dividend yield stays (by default): the price grows as the dividend does (p = g). It is the simplest way not to invent a price, and the page says so beside the result. In "More assumptions", a price growth of its own separates them.
• Dividend cut (a switch): the dividend falls by a percentage (30 % at first, as happened with many companies in 2009 and in 2020) at the start of the year chosen, and keeps growing from there: it does not go back by itself. If the yield stays, the price falls with it; with a price growth of its own, the price does not change.
• Tax: the percentage the person types, on each payment, before reinvesting. No country's tax is worked out: it depends on the country, the account and the treaties, and Horalis gives no tax advice.
• Inflation: 2 % a year at first, the ECB's target for the euro area since its 2021 strategy; the person can change it.
• The example the page opens with (10,000 to start, 200 a month, a 3 % yield, 3 % growth, 20 years, reinvesting) is round numbers so that a result shows, not a forecast or a recommendation.

Limits

• One portfolio with a steady yield and growth: no good and bad years but the cut chosen.
• Monthly payments: many shares pay each quarter or each year. With the same yield the year's total hardly changes; the effect of reinvesting is a little larger than with quarterly payments.
• No fees, no buying costs, no exchange rate.
• Neither the tax nor inflation changes over the years.

Tests that check it

calc.test.ts: 10,000 at 4 % pay 400 a year; the tax; reinvesting with monthly compounding; the steady yield (the value grows as the dividend does); a price growth of its own; the cut (that year and the next ones, and the price with it or not); monthly amounts; today's money; and what is not a plan (no answer).

Debatable

• Assuming a steady yield hides that share prices move much more than their dividends.
• A 30 % cut in a single year is an example, not the worst case.

Version of 23 October 2026.