Interest Capitalisation Calculator
Impact of capitalised interest on student or deferred loans.
Calculate impact of interest capitalisation on student loans and deferred-payment loans. See balance growth from unpaid interest.
What this tool does
Enter loan balance, rate, and deferral years. The tool shows balance after capitalisation period.
Enter Values
Formula Used
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Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
Interest capitalisation: unpaid interest added to principal, then earns more interest. Student loans, deferred loans, some construction loans capitalise. 30k student loan at 6% deferred 5 years: balance grows to 40k+ before any payments.
Run it with sensible defaults
Using loan balance of 30,000, annual rate of 6%, deferral years of 5, the calculation works out to 40,146.77. Nudge the inputs toward your own situation and the output recalculates instantly. The defaults are meant as a starting point, not a recommendation.
The levers in this calculation
The inputs — Loan Balance, Annual Rate, and Deferral Years — do not pull with equal force. Not every input has equal weight. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.
How the math works
Standard compound interest. Annual compounding of unpaid interest. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".
Using this to stay on track
The most common failure mode isn't the plan itself — it's letting the balance creep back up while you're paying it down. Set a rule: no new debt added to the same account until the balance is zero. The calculator is only useful if the number it shows doesn't keep resetting.
What this doesn't capture
Real payoff journeys include missed payments, fee changes, balance transfers, and promotional rates that reset. The calculation assumes a steady plan; reality is rarely that clean. Use the figure as the best-case plan against which actual progress gets measured.
Related calculations worth running
Plans get firmer when you triangulate. Alongside this one, the loan true cost calculator, the annual cost of credit calculator, and the auto loan comparison calculator tend to come up in the same conversations. Running two or three together exposes inconsistencies in any single assumption — which is usually where the useful insight lives.
Interest capitalisation produces balance based on the inputs provided.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
Standard compound interest. Annual compounding of unpaid interest.
References
Frequently Asked Questions
Should I pay interest during deferral?
When does capitalisation happen?
Can I prevent it?
Long-term impact?
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