Debt capacity calculator
Estimate an indicative monthly payment from income, essential expenses and existing debts, then translate it into approximate principal.
Budget headroom and ratio headroom
The payment is capped by the lower of actual budget headroom and the space within the selected debt ratio.
Target total ratio—
Additional payment—
Remaining monthly margin—
- Additional payment
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- Indicative principal
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- Remaining monthly margin
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- Additional payment
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- Indicative principal
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- Remaining monthly margin
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- Additional payment
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- Indicative principal
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- Remaining monthly margin
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- Additional payment
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- Indicative principal
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- Remaining monthly margin
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How capacity is estimated
Money left after essential expenses and current debts is calculated first. Separately, the tool finds the room left by the target debt percentage.
The indicative payment is the lower amount, so a seemingly acceptable percentage cannot ignore an already tight budget.
Advanced options provide a closer representation of the contract; keep their defaults when they do not apply.
Scenario formula
Payment = max(0, min(income − adjusted expenses − debts − buffer, income × ratio − debts)).
Example
With 3,000 income, 1,650 expenses, 300 existing debt and a 35% target, ratio room is 750 and budget room 1,050, so indicative payment is 750.
Frequently asked questions
Which ratio should I use?
There is no universal figure. Test several and retain a safety margin.
Gross or net income?
This tool uses net income because it also uses actual expenses; lender DTI metrics may use gross income.
Where does rent or mortgage go?
Use “Replace housing cost” only when that expense disappears with the new financing, avoiding double counting.
What is indicative principal?
The amount that would produce the payment at the entered rate and term, before fees.
Does positive capacity mean approval?
No. Credit history, security and lender policy are not assessed.