What if you invest £1,000 a month?
Nobody can tell you what a portfolio will return. What can be shown is what different assumptions produce — and what every compound interest calculator, including this one, quietly hides.
What the question is really asking
Search interest in “can I make £1,000 a month” and “what if I invest £1,000 a month” is enormous, and the two are almost opposites. One is asking for income now; the other is asking about accumulation over time. The second has a clean arithmetic answer. The first mostly doesn't.
Start with the honest version: nobody can tell you what a portfolio will return. What can be shown is what different assumptions produce, so you can see the shape of the thing rather than a promised number.
Try the arithmetic yourself
Illustrative arithmetic only, not a forecast or a projection of returns. It assumes a constant growth rate, which no real investment delivers, and ignores fees, taxes, inflation and the fact that markets fall as well as rise. Your actual outcome will differ.
Three things the calculator shows that people miss
Most of the ending figure is contributions, early on
For the first decade or so, what you put in dominates. Growth only overtakes contributions much later. That is why the amount you can consistently save matters more than the rate you assume, especially at the start.
The last decade does most of the work
Compounding is back-loaded. Cutting the time horizon by a third removes far more than a third of the ending value. Time in the market is not a slogan; it's where the arithmetic lives.
Small differences in rate become large differences in money
Two percentage points sounds trivial over one year and is enormous over thirty. This is also why fees matter: a 1.5% annual charge is a 1.5-point reduction in your assumed rate, every year, compounded.
Why a constant rate is a lie you should understand
The calculator assumes the same return every year. Real markets don't work that way — they deliver a scattered sequence of good and bad years, and the order matters. A severe fall early in the accumulation phase is largely recoverable because your later contributions buy in cheaply. The same fall just before you need the money is not.
The income version of the question
“How do I generate £1,000 a month?” is a different calculation: capital multiplied by yield. At a 4% dividend yield, £12,000 a year of income needs roughly £300,000 of capital. At 3%, closer to £400,000. There is no way around that arithmetic — and chasing a higher headline yield to shrink the number is the most reliable way to end up with less income, because unusually high yields usually signal a dividend the market expects to be cut.
What actually determines your outcome
In rough order of importance: how much you contribute, how long you leave it, what you pay in fees, and whether you stay invested through the falls. Stock selection matters, but it sits below all four of those, and no amount of good picking rescues someone who stops contributing or sells in a panic.
When you do pick individual companies
Oak Growth estimates what roughly 1,000 companies are worth and shows the gap against today's price, so the stock-picking part of the plan rests on a number rather than a hunch.
Explore Oak GrowthCommon questions
What if I invest £1,000 a month for 30 years?
Total contributions would be £360,000, and the ending value depends entirely on the growth rate you assume — the calculator on this page lets you test different assumptions. No rate can be promised; markets fall as well as rise, and real returns arrive in an uneven sequence rather than smoothly.
How much do I need to make £1,000 a month in dividends?
Capital multiplied by yield. At a 4% dividend yield you would need roughly £300,000 to generate £12,000 a year; at 3%, closer to £400,000. Chasing a higher headline yield to reduce the capital needed often backfires, since unusually high yields frequently precede a dividend cut.
Is investing monthly better than a lump sum?
Investing monthly removes the need to pick a moment and means you buy more units when prices are low. Historically, lump sums have often ended ahead on average simply because money is invested for longer, but monthly investing is what most people can actually do from income, and consistency matters more than optimisation.
Do compound interest calculators tell you what you'll get?
No. They apply a constant rate, which no real investment delivers. Actual returns arrive as an uneven sequence, and the order of good and bad years materially changes the outcome — particularly if a severe fall happens shortly before you need the money.
Also see: Dividend yield explained → · What is passive investing? → · Stocks and shares ISA explained →