SIP Annual Increase Calculator

500 a month growing 10% yearly for 20 years at 8% return: starts at 500, rising to about 3,058 a month by year 20, for a final pot of about 659,350. Annual step-ups track income growth, so the saving rate holds steady as pay rises. The resulting pot is larger than a flat contribution would produce, though most of that gap comes from paying in more rather than from stronger compounding.

Worked example

Starting monthly of 500, annual increase of 10%, 20 years and expected return of 8% produce a final pot of 659,349.89. Total paid in over the period is 343,650, so 315,700 of that pot is compound growth.

Which inputs move the result most

The sizes below are measured at the worked figures of 500 a month, a 10% annual increase, 20 years and 8% return, and each input moves on its own scale, so they indicate rough magnitude rather than a like-for-like ranking. Starting Monthly is exactly proportional at any scale: a 10% larger starting figure gives a 10% larger pot, 725,285. A percentage point on Expected Return adds about 66,000, against about 63,500 for a percentage point on Annual Increase %. Both are asymmetric upward, since a point removed costs less than a point added gains, the lost compounding falling on a smaller base. One more year is worth about 14.7% of the pot at 20 years, which makes Years the largest single lever at these figures. That lead narrows as the horizon lengthens, though: past roughly 26 years at these rates the two rate levers overtake it, and with a smaller step-up the crossover arrives sooner still, at about 19 years when the annual increase is 3%.

What's happening under the hood

The model runs month by month, not year by year. Each month the balance grows by one twelfth of the annual return, then the monthly contribution is added at month end. On each anniversary the contribution steps up by the annual increase, so the twelve payments of year two are larger than those of year one, and so on to the end of the horizon. Running it monthly rather than applying an annual average matters because the contribution base changes every year and growth compounds between step-ups.

Step-up against a flat contribution

500 a month rising 10% a year over twenty years at 8% reaches about 659,350. A flat 500 a month across the same period reaches about 294,510. The two differ by about 364,840, which the next section takes apart.

Attributing the difference

Of that 364,840 gap, 223,650 is extra money paid in: the step-up plan contributes 343,650 over twenty years against 120,000 for the flat one. That is 61% of the difference. The remaining 39% is compound growth on those extra contributions. The comparison is therefore between two different commitments rather than two ways of investing the same sum. The projection also holds the return constant and works before charges and tax.

Where this fits in planning

This is a "what-if" tool, not a forecast. It helps to test ideas: what happens to the result as the Starting Monthly or the Annual Increase % changes. A range of scenarios shows the spread of outcomes; a single answer does not.

What this doesn't capture

This is a simplified model that holds its assumptions constant. Real outcomes vary with market conditions, costs, taxes, and timing, so the figure is best read as one scenario rather than a forecast.

Where to go next

This calculation rarely sits alone in a planning exercise. The compound interest calculator isolates growth on a single lump sum, the investment return after fees calculator shows what charges take out of a projection like this one, and the monthly investment goal calculator works the other way round, starting from a target pot and solving for the contribution.