Robo vs DIY costs.

Robo-advisor vs self-investing calculator quantifies fee impact. Robo-advisors (Vanguard, Wealthfront, Schwab Intelligent Portfolios) charge 0.25-0.50% on top of underlying fund fees. Self-investing in same ETFs at 0.05-0.20% costs less. 100k over 30 years at 7%: 0.40% extra fee = 64k less terminal wealth.

Example: 100k invested 30 years at 7% gross. Self-allocate to Vanguard ETFs (0.10% expense ratio): 756k. Robo-advisor (0.50% total fees): 692k. Self-invest saves 64k - 8.5% more terminal wealth. The robo's value (rebalancing, tax-loss harvesting, simplicity) needs to add 0.40%/year to break even - high bar.

Robo value-add: (1) Automatic rebalancing (worth ~0.10-0.30% over decades), (2) Tax-loss harvesting (worth ~0.10-0.50% in taxable accounts), (3) Goal planning and behavioural support, (4) No-decision investing (worth a lot if alternative is cash sitting un-invested). For tax-advantaged accounts: self-invest wins easily. For taxable + behavioural support needs: robo can be worth it. Hybrid: self-invest core portfolio, use robo for taxable account + tax optimisation.

A worked example

Try the defaults: initial investment of 100,000, gross annual return of 7%, robo-advisor total fee of 0.4%, self-invest etf fee of 0.1%. The tool returns 59,844.90. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.

What moves the number most

The result responds to Initial Investment, Gross Annual Return %, Robo-Advisor Total Fee %, Self-Invest ETF Fee %, and Years. The rate and the time horizon usually dominate — compounding means a small change in either reshapes the final figure more than a similar shift in contribution size. Test this by doubling one input at a time.

The formula behind this

Compare future values at robo net rate vs self-invest net rate. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.

Using this well

Treat the output as one point on a wider map. Run it three times — a pessimistic case, a central case, and a stretch case — and plan against the pessimistic one. That habit alone separates people who stick with an investment plan from those who bail at the first wobble.

What this doesn't capture

Steady-rate math ignores real-world volatility. Actual returns are lumpy; sequence-of-returns risk matters most in drawdown; fees and taxes drag on compound growth; and behaviour changes in drawdowns can reduce outcomes below the projection. Treat the number as one scenario, not a forecast.