What is the difference between simple interest and compound interest?

Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus accumulated interest, so each period's interest is larger than the last. Over long periods, the difference is dramatic. A $10,000 investment at 6% simple interest earns $6,000 over 10 years. At 6% compounded annually, it earns $7,908.

What does compounding frequency mean?

Compounding frequency is how often interest is calculated and added to the principal. Monthly compounding adds interest 12 times per year; daily compounding does so 365 times. More frequent compounding produces a slightly higher effective annual yield than the stated nominal rate. At 6% nominal, monthly compounding gives 6.168% effective; daily gives 6.183%.

Does compounding frequency matter for GICs in Canada?

Yes. GIC interest is typically compounded annually or semi-annually. A GIC stated at 4.25% compounded semi-annually has an effective annual yield of (1 + 0.0425/2)^2 - 1 = 4.295%. When comparing GICs from different issuers, compare effective annual yields rather than nominal rates, because the compounding frequency varies.

How does investing in a TFSA change the compound interest calculation?

A TFSA does not change the compound interest formula, but it eliminates the tax drag on growth. In a non-registered account, interest income is fully taxable annually, which reduces the amount that compounds in subsequent years. In a TFSA, growth compounds on the full pre-tax amount each year. Over 30 years, this tax-free compounding can produce significantly more wealth than the same investment in a non-registered account.

What is a realistic long-term return assumption for Canadian investments?

Historical long-term returns for diversified Canadian equity portfolios (such as the TSX composite) have averaged roughly 7% to 9% annually including dividends, before fees and inflation. A balanced portfolio (60% equities, 40% fixed income) has historically returned approximately 5% to 7%. After inflation of 2% to 3%, real returns are lower. Conservative projections use 4% to 6%; aggressive projections use 7% to 9%.

Does starting later hurt compound growth as much as stopping contributions early?

Yes. The timing of money entering the account matters more than the timing of contributions stopping. A 25-year-old who contributes $200 per month for 10 years and stops, letting the balance compound for another 25 years at 7%, ends up with more than a 35-year-old who contributes $200 per month for 30 years. The first 10 years of compounding on early contributions drive outsized results.

What is the difference between nominal and real returns?

A nominal return is the stated percentage gain before accounting for inflation. A real return adjusts for inflation: real return approximately equals nominal return minus inflation rate. At 7% nominal and 2.5% inflation, the real return is approximately 4.5%. Financial planning that does not distinguish between nominal and real returns overstates future purchasing power.

How does compound interest apply to debt?

Compound interest works against you on debt. Credit card balances compounding at 19.99% monthly means interest is added to the balance monthly, and the next month's interest is calculated on a larger balance. The same compounding mathematics that builds wealth in savings accounts accelerates debt growth when balances are not paid in full.

What return rate should I use in the calculator for a GIC?

Enter the nominal annual rate stated on the GIC contract and select the matching compounding frequency (annually or semi-annually for most Canadian GICs). Do not use the effective annual yield and annual compounding together, as this double-counts the compounding adjustment. Use the nominal rate with the actual compounding frequency for an accurate projection.

Compound Interest Calculator

Calculate compound growth of savings with optional monthly contributions. Supports daily, monthly, semi-annual, and annual compounding.

Reviewed by Ben Stevenson, Editor Updated April 23, 2026 Source FCAC 2026

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Compound interest means earning interest on interest: the return earned in each period is added to the principal, and the next period’s return is calculated on the enlarged balance. Over time, this compounding produces exponential growth that far exceeds what simple interest would generate on the same contributions. This calculator models a starting balance with regular monthly contributions at a fixed annual return, across four compounding frequencies: daily, monthly, semi-annually, and annually.

How much does $10,000 grow at 6% over 20 years with monthly contributions?

A starting balance of $10,000 with $300 in monthly contributions at 6% annual return compounded monthly grows to approximately $157,000 after 20 years. Total contributions over the period: $10,000 plus $72,000 (240 months at $300) = $82,000. The remaining $75,000 is interest earned through compounding. The ratio of growth to contributions illustrates the core effect: contributions dominate in early years, but compounding growth overtakes them over time.

How compound interest is calculated

The compounding frequency effect

When interest is compounded more frequently, the effective annual yield exceeds the stated nominal rate. A 6% nominal rate compounded annually produces exactly 6.00% effective annual yield. Compounded monthly, the effective rate is (1 + 0.06/12)^12 – 1 = 6.168%. Compounded daily, the effective rate is (1 + 0.06/365)^365 – 1 = 6.183%. For most practical purposes, the difference between monthly and daily compounding is small, but the difference between annual and monthly compounding is meaningful over long time horizons.

The formula

For a starting balance P with regular monthly contributions C at a nominal annual rate r compounded n times per year, the monthly effective rate is: r_m = (1 + r/n)^(n/12) – 1. Each month, the new balance is the prior balance plus interest plus the contribution: balance_t = balance_{t-1} × (1 + r_m) + C. This is applied iteratively across all months in the projection period.

The Rule of 72

The Rule of 72 is a quick estimate of how long an investment takes to double: divide 72 by the annual return percentage. At 6%, money doubles in approximately 12 years. At 8%, it doubles in approximately 9 years. At 4%, approximately 18 years. The rule works for returns between roughly 4% and 15% and provides a useful mental check when comparing scenarios without a calculator.

Verified against source

Compound interest formula derivation: actuarial mathematics, standard reference is the Society of Actuaries Mathematics of Finance study materials. Effective annual rate formula: ISO 80000-2 standard notation. GIC rate disclosures: CDIC/FCAC guidelines for deposit investment products sold in Canada. TFSA and RRSP growth projections: no government-prescribed rate; illustrative rates are common in CRA publications.

Effective annual yield by compounding frequency at 6% nominal

Compounding frequency	Effective annual yield	$10,000 after 10 years (no contributions)
Annually	6.000%	$17,908
Semi-annually	6.090%	$18,061
Monthly	6.168%	$18,194
Daily	6.183%	$18,221

Worked example: TFSA invested in index funds over 30 years

A 30-year-old contributes $500 per month to a TFSA invested in a Canadian index fund returning 7% annually, compounded monthly. Starting balance: $0. Monthly rate: (1 + 0.07/12)^(12/12) – 1 = 0.5833%. After 10 years: approximately $87,000 (contributions: $60,000, growth: $27,000). After 20 years: approximately $262,000 (contributions: $120,000, growth: $142,000). After 30 years: approximately $613,000 (contributions: $180,000, growth: $433,000).

The same contributions without compounding (simple interest) would produce $180,000 plus 30 years of flat interest on the average balance, approximately $90,000 to $110,000 in interest: less than one-quarter of the compounded result. The compounding effect grows nonlinearly with time; the last 10 years of the 30-year scenario produce more growth than the first 20 years combined.

Rules and edge cases

Starting early matters more than contribution size

Time in the market amplifies compounding. A 25-year-old who contributes $200 per month for 40 years at 7% reaches approximately $528,000 (contributions: $96,000). A 35-year-old who contributes $400 per month for 30 years at 7% reaches approximately $490,000 (contributions: $144,000). The 25-year-old contributes $48,000 less but ends with more money, because the 10 extra years of compounding early in the growth curve are worth more than larger later contributions.

Inflation and real returns

The calculator projects nominal returns, which do not account for inflation. At 2% annual inflation, a 6% nominal return corresponds to approximately 4% real return (the purchasing power increase after inflation). A $157,000 projected balance in 20 years at 6% nominal represents approximately $106,000 in today’s purchasing power at 2% inflation. Long-term planning should distinguish between nominal and inflation-adjusted projections.

GICs and Canadian savings rates

Guaranteed Investment Certificates (GICs) are the most common fixed-return savings product in Canada. GIC interest is typically compounded annually or semi-annually. A 1-year GIC at 4.00% compounded annually earns exactly 4.00% effective. A 5-year GIC at 4.25% compounded semi-annually earns an effective 4.295% annually. Bank accounts and HISA rates change frequently with the Bank of Canada policy rate; the compound interest projection at today’s rate may not reflect returns over the full projection period.

Tax on investment growth

In a non-registered account, interest income is fully taxable in the year received. Dividends receive the dividend tax credit. Capital gains are partially included (50% for individuals up to $250,000 annually). The tax drag on compounding growth in a non-registered account significantly reduces after-tax returns. TFSAs eliminate this drag: growth is tax-free regardless of investment type. RRSPs defer tax until withdrawal. Using registered accounts maximizes the effective compounding rate by eliminating annual tax on growth.

Sequence of returns risk in longer projections

A flat annual return assumption smooths year-to-year volatility. In practice, investment returns vary: a 7% average over 20 years might include years of -20%, +25%, +12%, and so on. The order of returns matters more when withdrawals are being made (in retirement) than during the accumulation phase. During accumulation, regular contributions that buy more units in down years (dollar-cost averaging) partially offset sequence risk. The calculator models a flat return for simplicity; actual results will vary.

Frequently asked questions

What is the difference between simple interest and compound interest?: Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus accumulated interest, so each period's interest is larger than the last. Over long periods, the difference is dramatic. A $10,000 investment at 6% simple interest earns $6,000 over 10 years. At 6% compounded annually, it earns $7,908.
What does compounding frequency mean?: Compounding frequency is how often interest is calculated and added to the principal. Monthly compounding adds interest 12 times per year; daily compounding does so 365 times. More frequent compounding produces a slightly higher effective annual yield than the stated nominal rate. At 6% nominal, monthly compounding gives 6.168% effective; daily gives 6.183%.
What is the Rule of 72?: The Rule of 72 estimates how many years it takes for money to double at a given rate. Divide 72 by the annual return percentage. At 6%, money doubles in approximately 12 years. At 8%, approximately 9 years. The rule is a rough approximation that works well for rates between 4% and 15%.
Does compounding frequency matter for GICs in Canada?: Yes. GIC interest is typically compounded annually or semi-annually. A GIC stated at 4.25% compounded semi-annually has an effective annual yield of (1 + 0.0425/2)^2 - 1 = 4.295%. When comparing GICs from different issuers, compare effective annual yields rather than nominal rates, because the compounding frequency varies.
How does investing in a TFSA change the compound interest calculation?: A TFSA does not change the compound interest formula, but it eliminates the tax drag on growth. In a non-registered account, interest income is fully taxable annually, which reduces the amount that compounds in subsequent years. In a TFSA, growth compounds on the full pre-tax amount each year. Over 30 years, this tax-free compounding can produce significantly more wealth than the same investment in a non-registered account.
What is a realistic long-term return assumption for Canadian investments?: Historical long-term returns for diversified Canadian equity portfolios (such as the TSX composite) have averaged roughly 7% to 9% annually including dividends, before fees and inflation. A balanced portfolio (60% equities, 40% fixed income) has historically returned approximately 5% to 7%. After inflation of 2% to 3%, real returns are lower. Conservative projections use 4% to 6%; aggressive projections use 7% to 9%.
Does starting later hurt compound growth as much as stopping contributions early?: Yes. The timing of money entering the account matters more than the timing of contributions stopping. A 25-year-old who contributes $200 per month for 10 years and stops, letting the balance compound for another 25 years at 7%, ends up with more than a 35-year-old who contributes $200 per month for 30 years. The first 10 years of compounding on early contributions drive outsized results.
What is the difference between nominal and real returns?: A nominal return is the stated percentage gain before accounting for inflation. A real return adjusts for inflation: real return approximately equals nominal return minus inflation rate. At 7% nominal and 2.5% inflation, the real return is approximately 4.5%. Financial planning that does not distinguish between nominal and real returns overstates future purchasing power.
How does compound interest apply to debt?: Compound interest works against you on debt. Credit card balances compounding at 19.99% monthly means interest is added to the balance monthly, and the next month's interest is calculated on a larger balance. The same compounding mathematics that builds wealth in savings accounts accelerates debt growth when balances are not paid in full.
What return rate should I use in the calculator for a GIC?: Enter the nominal annual rate stated on the GIC contract and select the matching compounding frequency (annually or semi-annually for most Canadian GICs). Do not use the effective annual yield and annual compounding together, as this double-counts the compounding adjustment. Use the nominal rate with the actual compounding frequency for an accurate projection.

Methodology

The monthly effective rate is computed as (1 + annual_rate / n)^(n/12) - 1, where n is the compounding periods per year (365 for daily, 12 for monthly, 2 for semi-annual, 1 for annual). Each month, the balance is updated as prior_balance times (1 + monthly_rate) plus the monthly contribution. Total interest is ending balance minus starting balance minus total contributions made over the period.

Frequently asked questions

What is the difference between simple interest and compound interest?: Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus accumulated interest, so each period's interest is larger than the last. Over long periods, the difference is dramatic. A $10,000 investment at 6% simple interest earns $6,000 over 10 years. At 6% compounded annually, it earns $7,908.
What does compounding frequency mean?: Compounding frequency is how often interest is calculated and added to the principal. Monthly compounding adds interest 12 times per year; daily compounding does so 365 times. More frequent compounding produces a slightly higher effective annual yield than the stated nominal rate. At 6% nominal, monthly compounding gives 6.168% effective; daily gives 6.183%.
What is the Rule of 72?: The Rule of 72 estimates how many years it takes for money to double at a given rate. Divide 72 by the annual return percentage. At 6%, money doubles in approximately 12 years. At 8%, approximately 9 years. The rule is a rough approximation that works well for rates between 4% and 15%.
Does compounding frequency matter for GICs in Canada?: Yes. GIC interest is typically compounded annually or semi-annually. A GIC stated at 4.25% compounded semi-annually has an effective annual yield of (1 + 0.0425/2)^2 - 1 = 4.295%. When comparing GICs from different issuers, compare effective annual yields rather than nominal rates, because the compounding frequency varies.
How does investing in a TFSA change the compound interest calculation?: A TFSA does not change the compound interest formula, but it eliminates the tax drag on growth. In a non-registered account, interest income is fully taxable annually, which reduces the amount that compounds in subsequent years. In a TFSA, growth compounds on the full pre-tax amount each year. Over 30 years, this tax-free compounding can produce significantly more wealth than the same investment in a non-registered account.
What is a realistic long-term return assumption for Canadian investments?: Historical long-term returns for diversified Canadian equity portfolios (such as the TSX composite) have averaged roughly 7% to 9% annually including dividends, before fees and inflation. A balanced portfolio (60% equities, 40% fixed income) has historically returned approximately 5% to 7%. After inflation of 2% to 3%, real returns are lower. Conservative projections use 4% to 6%; aggressive projections use 7% to 9%.
Does starting later hurt compound growth as much as stopping contributions early?: Yes. The timing of money entering the account matters more than the timing of contributions stopping. A 25-year-old who contributes $200 per month for 10 years and stops, letting the balance compound for another 25 years at 7%, ends up with more than a 35-year-old who contributes $200 per month for 30 years. The first 10 years of compounding on early contributions drive outsized results.
What is the difference between nominal and real returns?: A nominal return is the stated percentage gain before accounting for inflation. A real return adjusts for inflation: real return approximately equals nominal return minus inflation rate. At 7% nominal and 2.5% inflation, the real return is approximately 4.5%. Financial planning that does not distinguish between nominal and real returns overstates future purchasing power.
How does compound interest apply to debt?: Compound interest works against you on debt. Credit card balances compounding at 19.99% monthly means interest is added to the balance monthly, and the next month's interest is calculated on a larger balance. The same compounding mathematics that builds wealth in savings accounts accelerates debt growth when balances are not paid in full.
What return rate should I use in the calculator for a GIC?: Enter the nominal annual rate stated on the GIC contract and select the matching compounding frequency (annually or semi-annually for most Canadian GICs). Do not use the effective annual yield and annual compounding together, as this double-counts the compounding adjustment. Use the nominal rate with the actual compounding frequency for an accurate projection.