Compound interest calculator
What a lump sum grows to over time — and, the part most calculators leave out, what it will actually buy once inflation has had its turn.
Last checked 20 July 2026 · free, no sign-up
Why the second number is the real one
Every compound interest calculator shows you a large ending figure. Very few show you what that figure is worth. In a country where inflation has run in double digits, the gap between those two numbers is not a rounding detail — it is most of the answer.
Pakistan's latest reported CPI is 11.1%, as of the desk's macro refresh on 2026-07-24. That is the bar. A return below it is a loss in purchasing power no matter how large the ending rupee figure looks, and the "in today's rupees" tile above is where you see it.
How the maths works
The calculator compounds monthly: the annual rate you enter is converted to its monthly equivalent, applied twelve times a year. Inflation is applied as a separate annual discount to produce the real-terms figure. Both are pure functions of the numbers you type — nothing is fetched, predicted, or assumed on your behalf.
The bars show contributions against total value year by year. Watch how long the dark portion dominates: compounding only becomes the larger half late, which is the actual argument for starting early rather than starting big.
What this calculator will not do
It will not tell you what return to expect, because that is not knowable. It will not tell you what to buy. Assumed returns are your assumption, and no market — least of all the KSE-100 — pays a steady rate. This is research tooling, not advice.
FAQ
Common questions
What return should I assume for PSX?
Nobody can tell you, and any calculator that fills this in for you is guessing. The KSE-100 has delivered very different returns depending on the decade you measure, and no market pays a steady rate. Run the calculator at two or three assumptions rather than one — the spread between them is the honest answer.
Why does the calculator show a second, smaller number?
That is the ending value in today's rupees, after inflation. It is the only figure that tells you what the money will actually buy. A nominal return of 12% in a year of 11% inflation is close to standing still, which the headline number hides.
Does this account for tax on gains?
No. This is a pure compounding calculation on the inputs you enter. Capital gains tax on listed Pakistani securities is deducted at settlement by NCCPL and depends on your filer status and when you acquired the shares, so it is handled separately.
Is monthly or annual compounding used?
Monthly. The annual rate you enter is converted to its monthly equivalent, which is the same method the Henneth desk uses internally, so the two always agree.
Other calculators
The desk
These numbers are the easy part
Henneth reads PSX companies in plain English — what the business earns, what it's worth, what changed this week. Research, not advice.