Karl's Mortgage Calculator review
A free, multi-platform calculator for detailed mortgage scenarios, including Canadian and UK modes.
Reviewed by iTechGuides Editors · Editorial team · Updated Nov 2026
Karl's Mortgage Calculator helps people calculate and compare mortgage payments across a range of loan structures. It is available on the web, Android, and iOS, with a free plan. The calculator covers core principal, interest rate, and term inputs, and can solve for one when the other three are provided. Its breadth makes it a fit for borrowers or small-scale users who need to examine more than a standard fixed-rate payment; anyone looking for a broader lending or financial-planning suite should look elsewhere.
The standout depth is in scenario modeling. Users can account for adjustable-rate changes, interest-only mortgages, and one-off, monthly, or annual extra payments, then examine payment and amortization results. Taxes, insurance, PMI, and HOA costs can also be included in estimates. The vendor site offers separate affordability and qualification calculators. This combination is useful when comparing loan structures or testing how extra payments and recurring costs affect an estimate, though outputs remain dependent on the assumptions entered.
Regional support is a notable distinction: the calculator supports Canadian mortgages and UK annual-rest mortgages alongside general mortgage calculations. That can suit people comparing scenarios across these conventions, while the web and mobile availability provides several access options. A separate Pro app is available as a one-time purchase, and its price differs between Google Play and the US App Store. Support is offered by email. Choose this calculator for detailed mortgage calculations across supported regions; choose another option if you need a broader financial tool or a single consistent Pro price across those stores.
Karl's Mortgage Calculator pros and cons
- Where it wins
- Reverse-calculate a loan input when the other three are known
- Model adjustable rates, interest-only loans, and extra payments
- Include taxes, insurance, PMI, and HOA costs in payment estimates
- Where it doesn't
- Loan estimates depend on the inputs entered
- Separate Pro app is a one-time purchase
- Support is limited to email
Karl's Mortgage Calculator fact sheet, pricing and score →
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