Monthly Income from Capital Calculator

Perpetuity yield on a managed portfolio

This calculator answers the classic "live off interest" question: how much income does capital C generate at net annual rate r, withdrawing only the yield so principal stays intact? Annual income is Y = C · r; monthly income is M = C · r / 12. This is a perpetuity in financial-math terms — the present value of a constant infinite cash flow is PV = M / i, hence M = PV · i.

Example: R$ 500,000 at a net 8% per year (typical for a diversified portfolio after taxes and fees) produces R$ 40,000 per year, or about R$ 3,333 per month. To safely pull R$ 10,000 monthly net (R$ 120,000/year) you need roughly R$ 1.5 million at the same 8%. The rate matters: at 10% net you'd need R$ 1.2 million; at 5%, R$ 2.4 million. Inflation is the silent killer of perpetuity strategies — if you spend the full nominal yield, real purchasing power decays at the IPCA rate (around 4% per year in Brazil).

Robo-advisors and managed portfolios in Brazil

Platforms like Magnetis, Vitreo (Empiricus), Warren, and Rico Inteligente automate diversified allocation across Tesouro, CDB, FIIs, and equity funds. Management fees range 0.3%–1.0% per year, versus passive ETFs (BOVA11, IVVB11) at 0.03%–0.20%. The fee gap compounds: 1% per year over 30 years removes roughly 26% of final wealth (0.99^30 ≈ 0.74). For a long-term perpetuity goal, low-fee passive allocation usually wins; managed services pay off when behavioral discipline (auto-rebalancing, tax-loss harvesting) outweighs the fee. The 4% safe withdrawal rule (Trinity Study, 1998) was calibrated for US 60/40 portfolios; in Brazil's higher real-rate environment 5%–6% has historically held over 30-year windows.

FAQ

What does "net rate" mean here? It's the yield after income tax, management fees, and custody. A 110% CDI gross at 15% Selic and 22.5% IR gives roughly 12.8% net; subtract 0.5% management and you're at 12.3% net. Always plug the post-everything number.

Why is monthly income just yearly divided by 12? The calculator uses a simple proportional split, common in financial planning. Strictly, monthly compounding would give a tiny premium — at 8% annual, the equivalent monthly is 0.643%, so R$ 500k × 0.00643 = R$ 3,216 (not R$ 3,333). The simple division overstates monthly income by ~3% at typical rates.

Does FGC cover this kind of portfolio? Only the CDB and LCI/LCA slices, up to R$ 250,000 per CPF per institution. Tesouro is backed by the Treasury (not FGC). Stocks, FIIs, and equity funds have no deposit insurance — they're market risk.

What happens if I withdraw more than the yield? Principal erodes and the timeline becomes finite — that's the depletion calculation, not perpetuity. Run both numbers before committing to a withdrawal strategy.