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Interest Reserve Runway Calculator
Interest reserves carry debt service during lease-up.
Runway months
32.7
Net monthly reserve burn
$55,000
Shortfall if stabilization missed
$0
How the math works
Net burn = debt service − NOI (floored at 0). Runway = reserve / burn.
$1.8M reserve. Net burn $55k/mo. Runway 32.7 months > 24 stabilization target — comfortable cushion.
EveryCalc calculators are designed for fast, practical estimates with transparent inputs and no required account. We use plain formulas, visible assumptions, and related tools so visitors can check the result from more than one angle.
Results are informational only. For financial, tax, legal, medical, construction, or other high-impact decisions, verify the output against primary sources or a qualified professional.
Learn more about our review process on the EveryCalc methodology page.
How this calculator works
What this page estimates
This Interest Reserve Runway Calculator is built to give a quick, browser-based estimate for interest reserve runway. Interest reserves carry debt service during lease-up. The inputs stay on the page during normal use, and the result should be treated as an estimate for planning, comparison, or education rather than professional advice.
Calculation approach
The calculator applies the standard relationship implied by the inputs, then formats the answer so it can be checked and reused. For finance tools, the most important step is using consistent units, rates, time periods, and assumptions before comparing the result with another calculator or outside quote.
Example workflow
For example, start with a realistic value you already know, change one input at a time, and watch how the answer moves. That makes it easier to tell whether the result is being driven by the main amount, the rate, the time period, or a unit conversion.
Practical checks
- Use current, real-world numbers when the result affects money, health, tax, or legal decisions.
- Run a low, base, and high case when the inputs are estimates.
- Check the related calculators below when the next decision depends on a different assumption.
How to interpret the interest reserve runway result
Best use
Use the result as a planning number for comparing payments, rates, returns, tax reserves, or cash-flow choices before you request a quote or make a commitment.
Cross-check
Compare the answer with the contract, lender estimate, tax form, brokerage statement, payroll record, or invoice that will control the real-world outcome.
Watch for
Do not rely on a single optimistic rate, return, or fee assumption. Money pages work best when you run low, base, and high cases and keep professional advice separate from the estimate.
This page belongs to the Finance calculator library, so the answer should be read in the context of the decision you are modeling rather than as a universal rule.
Before relying on this interest reserve runway estimate
Most calculator mistakes come from the inputs, not the arithmetic. Use this short audit before you reuse the answer in a spreadsheet, quote, application, or important conversation.
Confirm source numbers
Match balances, rates, fees, taxes, income, and payment dates against the lender quote, payroll record, tax form, statement, invoice, or contract.
Separate cash flow from total cost
A lower monthly payment can still cost more over time if fees, interest, taxes, or a longer term are hidden in the structure.
Run conservative cases
Test at least one higher-cost or lower-return case before using the output for a purchase, refinance, investment, loan, or tax decision.
Rerun this page when the rate, price, term, fee, tax rule, income, expense, or expected holding period changes.
How to Use
- Enter interest reserve balance.
- Enter monthly debt service.
- Enter NOI monthly contribution.
- Enter stabilization month target.
- Read runway and shortfall.
Frequently Asked Questions
What is interest reserve?
Dedicated loan proceeds set aside to pay interest during lease-up or construction. Lender sizes based on projected months to stabilization + cushion. Typical: 12-36 months of interest. Sized too small = mid-deal distress; too large = wasted loan proceeds.
How to size?
Projected interest expense × (months to stabilization + 6-month cushion). Conservative sponsors add 12 months cushion. Lender typically caps at 20-25% of loan (NCREIF benchmark). If math says more needed, loan is oversized for project.
What if depleted?
Interest reserve depletion = loan default trigger in most docs. Sponsor must fund additional capital or negotiate extension. Stabilization delay cascades: more TI, more LC, more carry. Prudent sponsors maintain 30%+ cushion vs base case projection.
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