Step-up SIP formula—calculate increasing SIP by hand

You should calculate one step-up SIP by hand—in your life

Rajkot CA student wanted the step-up SIP formula for an exam. Same formula builds real wealth.

Let S₀ = starting monthly SIP. Year k monthly SIP: Sₖ = S₀ × (1 + g)^k where g is annual step (0.08 for 8%).

Hold that tension. The pretty version comes later, if it survives.

In Rajkot this debate still shows up at dinners as if character, not cash flow, is the variable.

Numbers first. Feelings after the numbers get a chair.

Each month t, balance grows: B = (B + Sₖ) × (1 + r_m) with r_m = (1+r_annual)^(1/12) − 1 or r_annual/12 for rough work.

When the gap looks ugly, the gap is doing its job.

Nobody hands out a medal for pretending your Excel is braver than your salary.

Variables: S, g, r, n months

Build 10-row year table: year, monthly SIP, annual investment.

For each year add 12 months of FV annuity formula or month simulator.

Open a calculator and type the ugly version first—₹5k → ₹5.4k → ₹5.83k … small bumps compound to big corpus differences.

Type the version that would still stand after a bad bonus year.

Compare to step-up SIP calculator output—should match within rounding.

Ten-year manual table is tedious—that is why step-up SIP calculators exist.

If you cannot explain the result to a slightly impatient parent, you do not understand it yet.

Year loop + month loop

Using simple interest monthly. Use compound monthly at minimum.

Step-up mid-year but formula assumes January—align assumptions.

Mixing step-up SIP with separate lumpsum without tagging flows.

A rule of thumb is a starting fence, not a closing argument.

Your cousin’s 2017 small-cap luck is not a policy.

When the salary or the date moves, reopen the calculator. Do not recycle last year’s PDF.

People in Rajkot skip that and then call the failed plan “the market.” It was the skipping.

Shortcut: average SIP approximation (and its flaw)

Hand-calc one scenario; use calculator for sensitivity (8% vs 12% return).

For step-up + lumpsum, run two tabs or combined calculator if available.

Document step-up rule in SIP mandate where platform supports it.

Clear the 16% fire, keep oats, then argue about this. That sequence is not optional.

Investing while revolving a 36% card is theatre.

Cut the size before you cut the habit. Habits are expensive to rebuild.

A smaller SIP or a shorter loan goal beats a heroic screenshot you cancel in six weeks.

₹5,000 start, 8% step, 10 years, 11% return

₹5k start, 8% step, 10y, 11%: corpus often ₹11–13 lakh band (calculator confirms).

Flat ₹5k same period: ~₹10 lakh band—step-up wins on contributions.

Flat ₹7k start: similar to step-up path but front-loads pain.

Those are planning numbers, not a promise from a mutual fund or a bank RM.

If the plan only works at 18% returns or a 6% home loan forever, it is not a plan.

The bear version is the one you should be able to explain at dinner.

Keep a 10% haircut for tax, fees, or the extra month the builder delays.

Then let the calculator do goal planning

Formula is trust. Calendar is execution.

SEBI MF categories do not change the maths—only your fund choice does.

Quiet deposits look dull until they are the only thing that showed up.

Calendar reminder beats a quote about discipline.

A Rajkot cousin who wants a shortcut can get this page. They cannot get your leftover salary.

And please date your spreadsheet. Future you will not remember which fantasy version this was.

Use this to think. Use a human with a licence before you transfer.