Property development

Construction Interest Reserve Calculator

Estimate the reserve needed to fund interest during construction and lease-up. Enter your own assumptions and local rates.

What this calculator estimates

Estimate the reserve needed to fund interest during construction and lease-up. It combines the inputs below to produce Estimated interest reserve. Every assumption remains editable so the estimate can reflect the property, financing and location being evaluated.

Worked example

Using the displayed sample assumptions, the calculator produces $255,000. This is an illustration, not a market quote. Change one input at a time to understand what drives the result.

Inputs and assumptions

• Maximum loan balance — sample input: 2500000 currency units
• Average loan utilization — sample input: 55 %
• Annual interest rate — sample input: 8 %
• Construction period — sample input: 18 months
• Additional lease-up period — sample input: 6 months
• Average lease-up utilization — sample input: 90 %

How to interpret the result

Stress-test cost, timing, financing and stabilization assumptions. Compare a conservative case with an expected case and keep a record of the assumptions used.

Common mistake to avoid

Do not treat a preliminary budget as a guaranteed project cost. Local definitions, taxes, lending practices and measurement requirements can materially change the result.

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Reviewed 2026-09-08.