Investing
What is the P/E Ratio? How to Actually Use It
The price-to-earnings ratio is the most quoted number in investing, and the most misused. Learn what P/E really tells you, when it lies, and how to use it properly.
Jul 14, 2026 · 9 min read
The logic behind the deal.
Calculators for property deals, stock valuation and startup finance. Each one shows its formula and explains what the result means. Everything runs in your browser, and your numbers are never sent to a server.
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About this calculator
Compound interest
What it measures
Projects how a starting amount plus regular monthly contributions grows when returns are reinvested. Interest starts earning interest of its own, so growth accelerates the longer the money stays invested.
When to use it
Use it to plan long-term saving and investing: retirement accounts, index fund plans, or a child's education fund. Try doubling the time horizon and watch what happens to the interest share.
Watch out for
The rate you enter is an assumption, not a promise. Markets don't return a smooth 7% every year, and inflation quietly eats into the real value of the final number.
Compound interest
How savings and regular contributions grow over time.
€
€
%
years
Future value
In 20 yearsMost of the balance now comes from interest rather than deposits.Over 50% from interest
You contributed
Interest earned
59.88% of the final balanceEvery calculator, by field
Start with the most used tools below, or open a field to see everything in it.
Real estate
Yields, valuation, debt covenants and lease analysis for property deals.
- Cap rate check
- Rent vs. buy
- Mortgage amortization
- LTV & DSCR
- Net yield & cash-on-cash
- Residual land valuation
- 5-year mini-DCF
- Yield sensitivity matrix
Investing
Valuation, growth rates and portfolio risk for public-market investors.
- WACC
- CAGR
- Rule of 72
- Compound interest
- Sharpe ratio
- FIRE number
- Graham intrinsic value
- Enterprise value (EV)
Venture & PE
SaaS metrics, fundraising math and private-equity returns.
- LTV:CAC unit economics
- Pre-money vs post-money
- Dilution
- Burn rate & runway
- SaaS growth (MRR & ARR)
- CAC payback period
- Rule of 40
- SaaS magic number
A glossary that shows the math
160 terms in plain English. Every entry has a note on how it is used in practice, and the formula wherever one applies.
DSCR
Debt Service Coverage Ratio. How easily income covers mortgage payments.
NOI / AnnualDebtService
Banks demand >1.25x. If it drops below 1.0x, you are losing cash every month.
Latest guides
All 29 guidesInvesting
Dollar-Cost Averaging: How the Math Actually Works
DCA is the default advice for long-term investors. Here is the arithmetic behind it, when it beats lump-sum investing, and when it does not.
Jul 2, 2026 · 8 min read
Investing
What is WACC? The Discount Rate Explained Simply
WACC is the number every DCF hinges on, and most explanations make it harder than it is. Learn what the weighted average cost of capital means and how to calculate it.
Jun 18, 2026 · 8 min read