Interest Calculator
Project simple or compound growth with adjustable compounding frequency. Fully client-side — no account, uploads, or remote storage.
Added Apr 18, 2026 · Updated May 1, 2026
Input
Result
Enter a value for interest type to see your result.
How it works
Calculates simple and compound interest. Simple interest grows linearly on the principal. Compound interest earns interest on accumulated interest, growing exponentially.
Formula
Simple: Amount = P × (1 + r × t) Compound: Amount = P × (1 + r/n)^(n × t) Interest = Amount − P
- P
- Principal amount
- r
- Annual interest rate as a decimal (rate ÷ 100)
- t
- Time in years
- n
- Compounding frequency per year (e.g. 12 for monthly)
Step by step
- 01Choose Simple or Compound interest type.
- 02Enter your principal, annual rate, and time in years.
- 03For compound interest, select how often interest is compounded.
- 04Simple: Amount = P × (1 + r × t). Compound: Amount = P × (1 + r/n)^(n×t).
Examples
Simple interest: 8% on $10,000 for 5 years
10,000 × (1 + 0.08 × 5) = 14,000. Interest = $4,000.
Inputs
- Interest Type:
- 0
- Principal Amount:
- 10000
- Annual Rate (%):
- 8
- Time (years):
- 5
- Compounding Frequency:
- 1
Result
- Total Amount:
- 14000
- Interest Earned:
- 4000
Compound monthly: 8% on $10,000 for 5 years
10,000 × (1 + 0.08/12)^60 ≈ 14,898.46.
Inputs
- Interest Type:
- 1
- Principal Amount:
- 10000
- Annual Rate (%):
- 8
- Time (years):
- 5
- Compounding Frequency:
- 12
Result
- Total Amount:
- 14898.46
- Interest Earned:
- 4898.46
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus accumulated interest, so your money grows faster.
How does compounding frequency affect my returns?
More frequent compounding means slightly higher returns. Monthly compounding gives more than annual, and daily compounding gives the maximum for a given nominal rate.
Is the annual rate shown here APR or APY?
You enter a nominal annual rate and choose how often interest compounds. APY (annual percentage yield) bundles compounding into one comparable figure; APR often refers to loan costs including fees. For investments, compare like-for-like compounding assumptions.
Does this include taxes, inflation, or fund fees?
No. The math shows nominal growth of principal at the stated rate. Real purchasing power can be lower after inflation, capital gains tax, or management fees.
Can I model paying down debt with the same tool?
You can approximate savings growth, but loans with scheduled payments need an amortization model. Use the EMI or mortgage calculators for payment schedules and total interest on debt.