From a target to a monthly
How much to save each month to hit a savings goal
Most SA savers think in the wrong direction. They start with the monthly amount they can comfortably afford, save that, and see what it adds up to. Better question: what target do you actually want to hit, by when, and what monthly does that require? Knowing the answer changes the conversation from “saving what I can” to “saving what I need”.
The formula
Solving the future-value annuity formula for the monthly contribution (PMT):
PMT = (FV − PV × (1 + r)^n) × r ÷ ((1 + r)^n − 1)
FV = target, PV = current savings, r = monthly rate, n = months. The calculator above runs this for you. The intuition: subtract what your current savings will grow to on their own, then work out the monthly required to cover the remaining gap.
Why starting early matters this much
The same R500,000 target at 8% nominal return:
- 5 years: R6,790/month — R407,400 contributed.
- 10 years: R2,755/month — R330,600 contributed.
- 15 years: R1,470/month — R264,600 contributed.
- 20 years: R870/month — R208,800 contributed.
- 30 years: R340/month — R122,400 contributed.
The 30-year saver contributes a quarter what the 5-year saver does — and reaches the same target. The difference is purely compounding. Time isn’t just helpful; it’s the dominant variable.
Choosing a realistic rate
The rate matters but less than people think. Three reasonable defaults:
- Short horizon (1–3 years) — money market or savings account, ~5–8%. Cash is the right place; equities can swing too much over short periods to be reliable.
- Medium horizon (3–7 years) — balanced fund or unit trust, ~7–10%. Mix of equities, bonds, cash.
- Long horizon (7+ years) — equity-heavy via TFSA, RA, or unit trust, ~10–12% historical nominal. Volatile year-to-year but the time smooths it out.
When the monthly is unaffordable
Three levers, in order of how much they help:
- Extend the horizon. The single biggest lever. Going from 10 years to 15 years on a R500k target drops the monthly from R2,755 to R1,470 — almost half. Where possible, start long-horizon goals (retirement, kids’ education) early.
- Reduce the target. Some goals are more flexible than they feel. R500k for a deposit and R350k for a deposit are different goals worth comparing on impact.
- Accept higher expected returns. Moving from a 6% balanced fund to a 10% equity fund drops the required monthly meaningfully — at the cost of more volatility. Suitable for long horizons; risky for short ones.
If all three are maxed out and the monthly is still unaffordable, the goal genuinely needs to shrink. Better to plan a smaller realistic target than an aspirational one that doesn’t happen.
The TFSA priority
For most SA savers, the right contribution stack is:
- Tax-Free Savings Account — up to the annual contribution limit set by SARS. All growth is tax-free for life. Highest after-tax return available without extra risk.
- Retirement Annuity / pension — contributions are tax-deductible up to limits, growth tax-deferred. The tax deduction is itself a return.
- Taxable accounts— what’s left after the wrappers are maxed. Interest above the SARS exemption is taxed at marginal rate; CGT applies on equity gains; dividend tax on dividends. Lower after-tax return than wrappers.
The TFSA contribution limits change occasionally — verify the current annual and lifetime limits on sars.gov.za before relying on a calculation.
The automation move
The single most important thing you can do once you know the monthly: set up a debit order for that amount on the day after pay-day, going straight into your savings or investment account. Don’t leave it as a discretionary monthly decision. People reliably save more when the decision is made once, automated, and removed from the monthly conversation entirely.
If the calculator’s monthly is R1,500, set up the debit for R1,500 the day after pay-day. If you can’t afford R1,500, set up R1,200 — start. Adjusting the debit order upward later is easy. Starting from zero five years from now is harder.