Effective Interest Rate Calculator

The effective annual rate (EAR) tells you the true cost of a loan or the true return on an investment after accounting for how frequently interest is compounded. Financial products often quote nominal rates because they appear lower for borrowers and higher for savers. The EAR strips away this presentation choice and allows direct comparison. For example, a credit card charging 24 percent nominal with daily compounding has an EAR of 27.1 percent, substantially higher than the advertised rate.

Enter the nominal rate and compounding frequency to calculate the effective annual rate. The calculator also works in reverse, enter an effective rate and frequency to find the equivalent nominal rate. This is particularly useful when comparing products that disclose rates differently.

Comparing credit card, personal loan or mortgage offers with different compounding frequencies.
Converting a mortgage APR to an effective annual rate for accurate total cost comparison.
Evaluating savings account returns when different banks quote rates on different compounding bases.
Understanding the true cost of buy-now-pay-later products that quote monthly rates.

EAR (Effective Annual Rate): The actual interest rate earned or paid per year when compounding is factored in, always use EAR for product comparison.

APR (Annual Percentage Rate): A standardised disclosure rate required in many jurisdictions that accounts for fees and compounding to enable consumer comparison.

Daily Compounding: Interest calculated every day, produces the highest EAR for a given nominal rate and is common in credit cards and some savings accounts.

The most common mistake is comparing loan or savings products using nominal rates without adjusting for compounding frequency. A lender quoting 1.8 percent monthly is actually charging 23.9 percent EAR, substantially higher than a 20 percent nominal annual rate. Always convert to EAR before comparing.

Use with the Loan Calculator to compute total interest at the true effective rate. The Investment Calculator can project savings growth using the correct EAR rather than the nominal rate.

Frequently Asked Questions

A Sharpe ratio above 1.0 is generally considered good, meaning you earn more than one unit of excess return for each unit of risk. Above 2.0 is very good; above 3.0 is exceptional and often indicates either a genuinely superior strategy or measurement issues such as using too short a data period. Global equity indices have historically delivered Sharpe ratios of 0.3 to 0.5 over long periods. Hedge funds targeting Sharpe ratios above 1.0 are pursuing what most active managers cannot consistently sustain. When comparing funds or strategies, always use Sharpe ratios calculated over the same time period and benchmark.

Systematic risk, also called market risk, affects all investments and cannot be eliminated through diversification. Economic recessions, interest rate changes and geopolitical events are systematic risks. Unsystematic risk, also called idiosyncratic or specific risk, affects individual companies or sectors and can be reduced through diversification. Holding 20 to 30 uncorrelated stocks eliminates most unsystematic risk. The key insight from modern portfolio theory is that only systematic risk is compensated by higher expected returns, investors are not rewarded for taking unsystematic risk that could have been diversified away.

Value at Risk (VaR) estimates the maximum loss over a given period at a specified confidence level, for example, a 95 percent one-day VaR of €50,000 means you expect to lose no more than €50,000 on 95 out of 100 trading days. The critical limitation is that VaR says nothing about losses beyond the confidence threshold, the 5 percent of days not covered. In financial crises, losses frequently far exceed VaR estimates because the assumptions of normal return distributions break down precisely when tail risks materialise. VaR is best used as one risk metric among several, not as a standalone measure of portfolio risk.

A beta of 1.5 means your portfolio or investment moves 1.5 times as much as the market, in both directions. If the market falls 20 percent, a 1.5 beta portfolio would be expected to fall approximately 30 percent. High-beta portfolios outperform in strong bull markets and underperform significantly in bear markets. A beta below 1 indicates less sensitivity to market movements, defensive sectors like utilities and consumer staples typically have betas of 0.5 to 0.8. Beta is calculated from historical data and assumes the future relationship with the market will mirror the past, which is not always the case, particularly when a company's business model changes significantly.

CAPM remains the most widely taught and used framework for estimating the required return on an investment, despite well-documented empirical limitations. The model predicts that expected return equals the risk-free rate plus beta times the market risk premium. In practice, factors beyond beta, such as size, value, momentum and profitability, have been shown to explain additional return variation that CAPM misses. The Fama-French multi-factor models extend CAPM to capture these additional risk factors. For practical corporate finance and investment analysis, CAPM is used as a starting point and supplemented with judgment and sector-specific knowledge rather than applied mechanically.