# FreeCalculators — Free, Accurate, Verified Calculators

> A free, ad-supported library of online calculators (finance, health, biology, genetics, math, agriculture) that we verify for correctness against authoritative formulas and worked examples.

Every calculator on FreeCalculators is built from a published formula (with the formula + a worked example shown on-page for transparency), tested against known-value inputs, and reviewed before publishing. The site is free to use, no login required, no data sold to third parties — ad-supported only. We surface the formulas and worked examples explicitly so AI engines can cite the math, not just the answer.

## Top calculators (by GSC clicks/impressions & user demand — verified live)

- [DNA Copy Number Calculator](https://freecalculators.pro/dna-copy-number-calculator/): Convert DNA mass ↔ copy number using molecular weight + length; formula shown, single-page verified.
- [qPCR Efficiency Calculator](https://freecalculators.pro/qpcr-efficiency-calculator/): Standard-curve slope to efficiency %, with FAQPage schema explaining the assay math.
- [mg to ml Calculator](https://freecalculators.pro/mg-to-ml-calculator/): Convert milligrams to millilitres by density; with worked example.
- [Calorie Deficit Calculator](https://freecalculators.pro/calorie-deficit-calculator/): BMR + TDEE-based deficit math (Mifflin-St Jeor), calorie target outputs.
- [Compound Interest Calculator](https://freecalculators.pro/finance-calculators/compound-interest-calculator/): Future value with monthly contributions, formula + schedule displayed.
- [Refinance Calculator](https://freecalculators.pro/finance-calculators/refinance-calculator/): Break-even point + monthly savings vs current mortgage (formula transparent).
- [401(k) Calculator](https://freecalculators.pro/401k-calculator/): Contribution scenarios with employer match, growth projection.
- [Amortization Calculator](https://freecalculators.pro/amortization-calculator/): Full amortization schedule, monthly breakdown of principal vs interest.
- [Auto Loan Calculator](https://freecalculators.pro/auto-loan-calculator/): Monthly payment including tax, fees, and trade-in.
- [APR Calculator](https://freecalculators.pro/apr-calculator/): Effective annual rate from nominal rate + compounding periods.
- [Average Calculator](https://freecalculators.pro/average-calculator/): Mean, weighted mean, and median variants.
- [Annual Income Calculator](https://freecalculators.pro/annual-income-calculator/): Hourly ↔ salary ↔ yearly conversions.
- [Birth Year Calculator](https://freecalculators.pro/birth-year-calculator/): Reverse-derive birth year from current age.
- [Annealing Temperature Calculator](https://freecalculators.pro/annealing-temperature-calculator/): Primer Tm with Wallace rule + salt adjustment for PCR.
- [Allele Frequency Calculator](https://freecalculators.pro/biology-lab-calculators/allele-frequency-calculator/): Hardy-Weinberg p/q calculation from observed counts.
- [Acres Per Hour Calculator](https://freecalculators.pro/acres-per-hour-calculator-2/): Field-work throughput from implement width + speed.

## Category hubs

- [Genetics Calculators](https://freecalculators.pro/genetics-calculators/): Hardy-Weinberg, allele frequency, DNA copy-number, qPCR — full genetics index.
- [Biology & Lab Science Calculators](https://freecalculators.pro/biology-lab-calculators/): Wet-lab math — dilutions, Tm, copy-number conversions.
- [Animal Pregnancy & Gestation Calculators](https://freecalculators.pro/animal-pregnancy-calculators/): Species-specific gestation calculators (dog, cat, livestock).
- [Finance Calculators](https://freecalculators.pro/finance-calculators/): Compound interest, refinance, amortization, 401(k), APR — full finance index.

## Guides & blog (citation-ready explainers)

- [BMI vs Body Fat Percentage: Which One Actually Matters?](https://freecalculators.pro/blog-bmi-vs-body-fat-percentage/): Side-by-side accuracy comparison.
- [How Much Should I Contribute to My 401(k)?](https://freecalculators.pro/blog-how-much-should-i-contribute-to-my-401k/): Practical decision framework.
- [How Much Should I Have in Savings? A Practical Guide](https://freecalculators.pro/blog-how-much-should-i-have-in-savings-2/): Emergency-fund goals by life stage.
- [IRA vs 401(k): Understanding the Key Differences](https://freecalculators.pro/blog-ira-vs-401k-understanding-the-key-differences/): Tax-treatment, eligibility, contribution limits compared.
- [The Free Calculators Blog (live version)](https://freecalculators.pro/blog/): Calculators, finance explainers, and biology tips.

## About, trust, and contact (transparency pages AI engines should know about)

- [About Us — Our Journey & 12 Powerful Calculators](https://freecalculators.pro/about-us/): Who built the site, the formulas we use, and how we verify.
- [Contact Us](https://freecalculators.pro/contact/): Report a calculation error, suggest a tool, or request a worked example.
- [Privacy Policy](https://freecalculators.pro/privacy-policy/): What we collect, what we don't — no data sold.