Money math you can actually trust.
Ten clear, transparent calculators for loans, savings and everyday money decisions. Every formula is shown, every number is computed on your device.
No ads, no cookies, no data leaves your browser.
Calculators
Every tool, grouped by what you’re planning
Pick a calculator, adjust the inputs, and see the result and the working instantly.
Loans & mortgages
Savings & growth
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Compound Interest Calculator
See how savings grow with compounding and regular monthly contributions.
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Inflation & Purchasing Power Calculator
Estimate future costs and how inflation erodes the value of money.
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Savings Goal Planner
Find the monthly amount you need to save to reach a target by a deadline.
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Percentage Change & CAGR Calculator
Measure total percentage change and compound annual growth rate.
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Rule of 72 Doubling-Time Estimator
Estimate how long it takes money to double at a given rate, or the rate needed.
Everyday money
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Break-even & Contribution Margin Calculator
Find how many units you must sell to cover fixed costs or hit a profit target.
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Currency Converter (Manual Rate)
Convert amounts using an exchange rate you enter. No live data.
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Tip & Bill Split Calculator
Work out the tip, total and each person's share of a bill.
Why LedgerLab
Built to be checked, not just believed.
No lead forms, no upsells. Just honest math that respects your privacy.
Private by design
Every calculation runs locally in your browser. Nothing you type is stored, tracked or sent anywhere.
Verified formulas
Standard, textbook formulas — shown and explained on every page so you can check the working.
Instant results
Results update as you type, with full year-by-year and month-by-month schedules where it matters.
Works on mobile
Clean, responsive layouts with large touch targets that work just as well on a phone as a desktop.
Methodology
How we calculate
Each calculator uses a standard, well-documented formula — the same ones taught in finance courses and used in lender disclosures. We keep the models simple on purpose so you can follow every step.
Results are estimates for education. Real products include taxes, fees and changing rates. Read the disclaimer.
- 1Standard formulasAmortisation, compound growth, CAGR and doubling time use their textbook definitions, written out on each page.
- 2Month-by-month steppingWhere schedules matter, we step through every month so balances, interest and payoffs line up with real statements.
- 3Validated inputsOut-of-range or missing values get a friendly message instead of a misleading number.
- 4Reviewed regularlyEvery tool page shows when it was last reviewed. Last review: October 2026.
All tools are for educational purposes only and are not financial advice. Read the full disclaimer.