Free financial calculators, built for everyday decisions

What is Matharb?

Matharb started as a single tool for checking whether a US-traded ETF was priced fairly relative to its underlying holdings. It has since grown into a small suite of financial calculators covering some of the most common questions people have about their money: how an investment compounds over time, what a mortgage actually costs, whether a rental property pencils out, and whether retirement savings are on track.

Every tool runs entirely in your browser. There's no account, no email capture, and no tracking of your personal financial inputs.

What Matharb offers

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  ETF fair value checker Compare a US-traded ETF's market price to the weighted performance of its underlying holdings to spot a premium or discount.
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  Compound interest & DCA tools Visualize how contributions grow over time, and compare dollar-cost averaging against investing a lump sum at once.
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  Mortgage & property calculators Estimate monthly payments, full amortization schedules, and rental property returns including cap rate and cash-on-cash return.
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  Retirement, loan & dividend tools Check if your retirement savings are on track, see how extra loan payments save interest, and project dividend income over time.
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  Privacy first No account required and no personal financial data collected. Enter your numbers and get an answer.

Important disclaimer

Matharb's tools are for educational purposes. The data and results they provide are not financial advice and should not be used as the sole basis for any investment, borrowing, or retirement decision. Market data may be delayed or inaccurate, especially outside of regular US trading hours.

Always do your own research and consult a qualified financial advisor before making financial decisions.