About this tool
Black Friday, a new phone, a sofa: is it better to take the cash discount or pay in instalments 'interest-free'? Type the cash price, the number of instalments and their value. The calculator brings the instalments to today's money at the rate your savings would earn meanwhile (by default Brazil's CDI rate of the day, from the Banco Central, minus about 20% income tax) and tells you which option is cheaper and by how much. It also shows the interest hidden in the instalment plan compared with the cash price. Runs in your browser.
How to use it
- 1 Type the cash price, with any discount.
- 2 Type the number of instalments and the value of each.
- 3 Choose whether the first instalment is today or in 30 days.
- 4 Adjust what your money earns and read the best option and the hidden interest.
Frequently asked questions
If the instalments are interest-free, is paying in instalments always better?
Only when there is no cash discount: then the money you keep invested earns something while you pay. With a cash discount, compare the hidden interest with what your money earns.
What is the hidden interest?
The monthly rate at which the instalments would be worth exactly the cash price. A 'free' plan of 10 × 200 against 1,900 in cash hides about 0.94% a month.
Why use the CDI?
It is the benchmark rate for post-fixed investments in Brazil (CDBs, Tesouro Selic). If your money earns a different rate, type yours.
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