Deposit vs. Savings Interest Comparison Calculator
Compare simple and compound after-tax payouts on lump-sum deposits and monthly savings plans
Enter a lump-sum principal, a monthly contribution, interest rates, a term, and a tax option, and this calculator works out simple and compound interest for both a fixed deposit (lump sum) and an installment savings plan (monthly contributions), then compares the after-tax payouts side by side. It's built for anyone deciding whether to park a lump sum or save monthly, and for anyone curious how rates and tax treatment change what actually lands in their account. Everything is calculated instantly in your browser, so the amounts you enter are never sent to a server.
🔒 Everything runs 100% in your browser. Your files and input are never uploaded to any server.
How to use
- Enter the lump-sum principal and annual rate for the fixed deposit
- Enter the monthly contribution and annual rate for the installment savings plan
- Choose the term in months and the tax option: standard tax, preferential tax, or tax-exempt
- Review the simple and compound after-tax payouts in the comparison results and copy them if you need to
FAQ
- Is interest calculated differently for a fixed deposit and an installment savings plan?
- Yes. A fixed deposit puts the whole principal in at once, so it earns interest for the full term. An installment plan adds money each month, so later contributions earn interest for a shorter time — meaning the same rate yields less total interest than a fixed deposit.
- How do simple and compound interest differ here?
- Simple interest accrues on the principal only. With compound interest, each month's interest is added to the balance and earns interest itself the following month, so the longer the term, the more compound interest pulls ahead.
- What do the tax options mean?
- They set how interest income tax is applied. You can choose Korea's standard rate (15.4%), the preferential rate (9.5%), or tax-exempt (0%). The selected rate is deducted from pre-tax interest to give the after-tax payout.