Savings & Deposit Calculator API

Compute term-deposit interest as Vietnamese banks pay it: at maturity, monthly or upfront, with rollover of principal or principal + interest, and monthly savings plans.

GETPOSThttps://apibox.io.vn/v1/savings-calc

Data & JSON▶ Try it online

The savings calculator computes what a bank deposit earns. For a term deposit give the amount, the yearly rate and the term (term_months); interest can be paid at maturity (interest=end, lãi cuối kỳ), every month (monthly) or upfront (upfront, lãi trả trước, discounted as P·r·t / (1 + r·t)). Over a longer horizon (months) the deposit rolls over: with rollover=principal_interest interest is added to the principal at each renewal (compounding), with principal it is paid out.

For a regular savings plan (monthly_deposit, gửi góp) the API adds the deposit every month and compounds monthly. The response gives the total interest, the final balance, the total received and the effective annual yield, plus the schedule by period or by month, so offers with different terms and payment methods can be compared.

The calculation uses the simple monthly convention (rate / 12 × months). Banks count actual days (rate × days / 365), so real amounts can differ slightly; early withdrawal usually earns only the demand-deposit rate. Interest on bank deposits is exempt from personal income tax in Vietnam.

Parameters

Name	In	Type	Required	Default
`amount`	body\|query	number	no		Initial deposit.
`rate`	body\|query	number	yes		Yearly interest rate in %.
`term_months`	body\|query	number	no	`12`	Term of the deposit (0 = demand).
`months`	body\|query	number	no		Total horizon in months (rollovers).
`interest`	body\|query	string	no	`end`	`end`, `monthly` or `upfront`.
`rollover`	body\|query	string	no	`principal_interest`	`principal_interest`, `principal` or `none`.
`monthly_deposit`	body\|query	number	no		Regular monthly deposit (savings plan).

Example

curl "https://apibox.io.vn/v1/savings-calc?amount=100000000&rate=6&term_months=6&months=24" \
  -H "Authorization: Bearer YOUR_API_KEY"

const res = await fetch('https://apibox.io.vn/v1/savings-calc?amount=100000000&rate=6&term_months=6&months=24', {
  method: 'GET',
  headers: {
    Authorization: 'Bearer YOUR_API_KEY',
  },
});
const data = await res.json();
console.log(data);

import requests

res = requests.get(
    "https://apibox.io.vn/v1/savings-calc?amount=100000000&rate=6&term_months=6&months=24",
    headers={"Authorization": "Bearer YOUR_API_KEY"},
    timeout=30,
)
print(res.json())

<?php
$ch = curl_init('https://apibox.io.vn/v1/savings-calc?amount=100000000&rate=6&term_months=6&months=24');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['Authorization: Bearer YOUR_API_KEY'],
]);
$response = curl_exec($ch);
print_r(json_decode($response, true));

Response

{
  "mode": "term_deposit",
  "amount": 100000000,
  "rate": 6,
  "term_months": 6,
  "months": 24,
  "interest_payment": "end",
  "rollover": "principal_interest",
  "total_interest": 12550881,
  "interest_paid_out": 0,
  "final_balance": 112550881,
  "total_received": 112550881,
  "effective_annual_yield": 6.09,
  "tax_on_interest": 0,
  "periods": [
    {
      "period": 1,
      "from_month": 1,
      "to_month": 6,
      "principal": 100000000,
      "interest": 3000000,
      "paid_out": 0,
      "balance": 103000000
    },
    "…"
  ],
  "note": "Simple monthly convention …"
}

Use cases

Savings calculators on bank and fintech websites
Compare term deposit offers (end vs monthly vs upfront interest)
Plan regular savings goals
Personal finance apps and spreadsheets

FAQ

End of term or monthly interest?

Interest at maturity usually has a slightly higher rate and compounds when rolled over; monthly interest gives regular cash flow at a slightly lower rate.

How is upfront interest computed?

Paid at the start, it is discounted: P × r × t / (1 + r × t), so it is a bit less than the end-of-term amount at the same rate.

Is interest taxed?

No, interest on deposits at credit institutions is exempt from personal income tax in Vietnam.

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Savings & Deposit Calculator API

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Response

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