Super DIY Calculator Notes

This post is mainly for us as we’re testing AI on certain calculations for brainstorming purposes. Currently, AI has their own default methods when projecting, but when factchecking certain projections, their initial method is off, so we’ll have to retrain AI into correcting their projections in our assessment.

// Test 1: Test apply growth rate at the end of year including contribution //

When calculating the crossover point where net contributions (we’ll use non-concessional contributions first), equals to growth (we’ll default this at 5%), we told AI to estimate and forecast about what Age I would be, and estimate the super balance during the crossover point. When factchecking, AI stated this:

// AI Response //

❗ Why my earlier number was off

I mistakenly applied growth to the opening balance before contributions — which is a valid method in some contexts (e.g., lump‑sum contributions at year‑end), but not for super.

And the 197K figure was simply incorrect — thank you for catching it.

/ My calculation /

Opening balance + non-concessional contribution = A1*(1+GR)=A2

Although it’s not 100% since this would assume that the contribution is made right at the beginning of the year to capture the full annual growth, however, it’s better than AI assuming growth calculation on the opening balance, therefore, double counting the growth at the initial.

An option we could consider is calculating average growth and not the full growth since the contribution can be anytime during the year. Prefer not to prorate as results can be skewed and harder to factcheck.

/ AI Method B //

Method B — Growth first, then contributions

This is equivalent to saying:

“All contributions are made on 30 June.”

Which is not how super works in reality.

🎉 Final takeaway

Method B is not “wrong” — it just represents a different economic reality. A reality that does not match how super works.

Your instinct was correct: Method A is the right method for your calculator.

// Test 2: What's the estimated growth $ at retirement and preservation age? //

// AI Response //

1. Growth $ at Retirement (Age 55)

This is the amount your super earns in the year you retire, assuming no contributions after 55.

2. Growth $ at Preservation Age (60)

This is the amount your super earns in the year you reach age 60, with no contributions between 55–60.

// My question //

Is CAGR% included?

// AI Response //

🎯 1. CAGR only applies when there are no contributions

CAGR is defined as:

CAGR=(Ending ValueStarting Value)1/n−1

🎯 2. Your calculator uses a Future Value (FV) model, not CAGR

Your projection is built from:

FV=S0(1+g)n+C(1+g)n−1g

This is:

• FV of a lump sum

• • FV of an annuity (your contributions)

This is the correct method for superannuation.

CAGR is not part of this logic.

🎯 3. Even if we forced a CAGR, it would be meaningless

If you tried to compute:

(504K170K)1/11−1

You would get a number — but it would be wrong, because:

• The 504K includes contributions

• CAGR would treat contributions as “growth”

• It would inflate the apparent return

• It would mislead the user

This is why professional super calculators never show CAGR.

// My notes //

Point 3 is quite interesting. Something to consider is that Super obviously includes contributions, so trying to calculate actual growth is like finding a needle in the haystack. Even if we manage to calculate the growth for one year, we’ll have to remove contributions every year and calculate growth again and so on, so we’ll most likely exclude calculating CAGR for Super, but we’ll consider calculating CAGR for our net worth instead.