An annuity is a series of equal payments at a fixed interest rate. Saving into one, the future value is the payment times ((1 + i)^n − 1) ÷ i, where i is the rate per period and n the number of payments; paying out of one, the payment a lump sum supports is the lump sum times i ÷ (1 − (1 + i)^−n). Payments at the start of each period (an annuity due) earn one extra period of interest. A third mode solves for n, how long a lump sum lasts.
With the defaults, 500 at the end of each month for 20 years at 5% grows to 205,516.83 from 120,000 of payments. Paid out instead, 500,000 at 5% supports 3,299.78 a month for 20 years, and 3,000 a month lasts 23.76 years: 285 full withdrawals and a final 427.00.
The rate is a nominal yearly rate divided by the number of payments a year. Insurance annuity fees, surrender charges, taxes and inflation are not included.
Exemplos resolvidos
Future value of 1,000 a year for 10 years at 5%
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Future value of regular payments
Payment each period
1000
Starting balance
0
Term
10
Term in
Anos
Interest rate (per year)
5%
Payments every
Ano
Payments made at
End (ordinary)
Future value
12,577.89
Total of all payments
10,000.00
Interest earned
2,577.89
Fonte de verificação: Future value annuity factor table, 5% and 10 periods: 12.5779; Python decimal 12,577.8925355…
Excel FV example: 500 now plus 200 at the start of each month, 6%, 10 months
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Future value of regular payments
Payment each period
200
Starting balance
500
Term
10
Term in
Meses
Interest rate (per year)
6%
Payments every
Mês
Payments made at
Start (annuity due)
Future value
2,581.40
Fonte de verificação: Microsoft FV documentation: =FV(0.06/12, 10, -200, -500, 1) returns $2,581.40
Excel PV example reversed: 59,777.15 paid out monthly for 20 years at 8%
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Payout from a lump sum over a set time
Lump sum at the start
59,777.15
Term
20
Term in
Anos
Interest rate (per year)
8%
Payments every
Mês
Payments made at
End (ordinary)
Payment each period
500.00
Fonte de verificação: Microsoft PV documentation: =PV(0.08/12, 12*20, 500, , 0) returns ($59,777.15)
Perguntas
How do you calculate the future value of an annuity?
Multiply the payment by ((1 + i)^n − 1) ÷ i, where i is the rate per period and n the number of payments. 1,000 at the end of each year for 10 years at 5% grows to 1,000 × 12.5779 = 12,577.89; paid at the start of each year (an annuity due) it grows to 13,206.79, 5% more, because every payment earns one more year.
How much does an annuity pay per month?
Divide the lump sum by the present-value factor (1 − (1 + i)^−n) ÷ i. 500,000 at 5% a year (0.4167% a month) paid over 20 years gives 3,299.78 a month, 791,946.89 in total. Microsoft's PV documentation gives the reverse: 500 a month for 20 years at 8% costs 59,777.15 today.
How long will a lump sum last with monthly withdrawals?
Solve n = −ln(1 − P·i ÷ W) ÷ ln(1 + i), with P the lump sum, i the monthly rate and W the withdrawal. 100,000 at 6% with 1,000 taken at the end of each month lasts 138.98 months: 138 full payments and a final 975.78, about 11.6 years. If W is no more than P·i (500 here), the balance never runs out.
What is the difference between an ordinary annuity and an annuity due?
An ordinary annuity pays at the end of each period, like loan repayments; an annuity due pays at the start, like rent. An annuity due is worth (1 + i) times the ordinary one, both in future value and in present value. At 5% a year, a 10-year annuity due of 1,000 accumulates 13,206.79 against 12,577.89.
Qual é a precisão de “Annuity calculator (growth and payout)”?
A precisão depende dos dados inseridos e das hipóteses do método. O cálculo decimal usa 50 algarismos significativos, mas estimativas, métodos numéricos e dados de origem podem ter menor precisão; o arredondamento exibido não elimina essas limitações. Exemplos resolvidos verificados com fontes independentes: 8. Por exemplo, “Future value of 1,000 a year for 10 years at 5%” é verificado com Future value annuity factor table, 5% and 10 periods: 12.5779; Python decimal 12,577.8925355….
De onde vem o método?
Microsoft Excel FV, PV, PMT and NPER functions (type 0 = end, 1 = start of period); Kellison, The Theory of Interest, 3rd ed., ch. 3 (annuities-immediate and annuities-due).
Kellison, The Theory of Interest, 3rd ed., ch. 3 (annuities-immediate and annuities-due)
Apenas para planejamento. Credores, autoridades fiscais e mercados aplicam seus próprios arredondamentos, tarifas e regras; confirme os valores com eles antes de assumir um compromisso.
Verificado com as referências
Esta calculadora inclui 8 exemplos resolvidos com respostas de fontes independentes. Eles fazem parte do conjunto de testes e você também pode executá-los aqui.