Interest Reserve Calculator
Size a construction or rehab interest reserve month by month and test if it will last
Install it in one line — paste a single command into Claude, ChatGPT or Cursor and it writes the skill into your project.
Free, and about thirty seconds: a work email and a six-digit code.
Downloading shares your name, firm, role, and email with The Helvetica Group. That introduction is what keeps every skill here free.
What this skill does
Works out how much interest reserve a construction or rehab loan really needs, month by month from the draw schedule, and warns you early when a loan already funding is going to run out.
What it does
- Builds a month-by-month table of loan balance, interest, and reserve remaining
- Explains and compares the two ways interest is charged — on the full loan amount from day one (Dutch) or only on money actually advanced (non-Dutch) — and shows what the difference costs
- Sizes the reserve through the expected sale or refinance plus cushion months, and rounds up
- Re-tests a reserve on a loan in progress when the schedule slips, and shows the month it runs dry and the dollar shortfall
- Checks whether payoff plus cushion lands before or after maturity
When to use it
- You are structuring a construction, ground-up or rehab loan
- A borrower asks why the reserve is the size it is
- A project has slipped and you need to know if the reserve still covers it
- Before approving a change order or extension that adds months
What to have ready
- The day-one advance and the holdback amount
- The draw schedule or build timeline
- The rate and whether interest is charged on the full loan or only on money advanced
- The expected payoff month and the loan term
How to use it
- Download it with the button above. You'll sign in with a work email — that's how the creator knows who is using their skill.
- Copy the install prompt from the "Run it in Claude" box, and paste it into Claude along with the file. Claude installs the skill, fills in your firm's details where the file has
[BRACKETED]placeholders, and runs a quick test with you. - Then just ask in plain English. Claude picks the skill up on its own when a request matches it. Anything it still needs, it asks you for — it won't invent a number.
"Size the interest reserve on [ADDRESS]: [INITIAL ADVANCE] at closing, [HOLDBACK] drawn over [MONTHS] months, [RATE]% interest on funds disbursed, sale expected month [MONTH]."
What you get back
A reserve figure (exact and rounded), a month-by-month table, a side-by-side of both interest methods, a pass or fail depletion test with the shortfall, and a plain-English note you can share with the borrower.
Good to know
- Output quality tracks input quality. A missing figure is flagged as missing — it is never estimated to fill a gap.
- Every draft is a starting point for your own review, not a finished decision.
- Runs anywhere Claude does: the Claude app, Claude Desktop, or Claude Code.
- Every assumption — draw timing, day count, cushion months — is printed on the output so the numbers can be checked and changed.
Legal disclaimer
This skill drafts; it does not decide. Its output is not legal, tax, accounting, appraisal, or investment advice, and using it creates no attorney-client, fiduciary, or advisory relationship. Nothing it produces is a commitment to lend or an offer to sell a security. Verify every number, date, citation, and conclusion against the source documents, and have a qualified professional licensed in the relevant jurisdiction review the work before you rely on it or send it to a borrower, investor, counterparty, or regulator. Laws, rates, and market data change. The final work product is yours.
Inside this skill
The actual file you get. Members can read it in full before saving it.
Interest Reserve Calculator
The interest reserve is the part of a construction or rehab loan that pays the lender's interest while the property earns nothing. Size it too small and the borrower is writing checks from outside cash by month nine — or, worse, not writing them. Size it by rule of thumb and it will be wrong in whichever direction the schedule moves. This skill builds the reserve month by month from the actual draw curve, shows the difference between the two ways interest is charged, and re-tests the reserve on loans already funding.
Works for: ground-up construction, heavy rehab and fix-and-flip holdbacks, value-add bridge loans with future funding, and land-development loans with a funded reserve. It is the calculation engine behind ground-up-construction-underwriter and change-order-evaluator; it does not review draws (see construction-draw-reviewer).
Step 1 — Intake
| Input | Required? | Notes |
|---|---|---|
| Initial advance at closing | ✅ | Purchase or land advance, plus any fees or costs financed on day one |
| Future funding (holdback) and its draw curve | ✅ | By month: from the draw schedule, the builder's schedule of values, or an even spread if nothing better exists (label it) |
| Note rate | ✅ | Fixed, or index + margin with the index assumption stated |
| Interest method | ✅ | Dutch (interest on the full commitment) or non-Dutch (interest on funds disbursed). Read the note or term sheet — do not assume |
| Day-count convention | Helpful | 30/360, actual/360, or actual/365. Default to 30/360 and say so |
| Term and extension options | ✅ | Maturity month; extension length and fee |
| Projected payoff month | ✅ | Construction months + sale closing or refinance month |
| Cushion months | Helpful | Illustrative default 2–3 months beyond projected payoff; replace with policy |
| Does the reserve itself accrue interest? | Helpful | On nearly every loan, yes — each monthly interest payment from the reserve is a disbursement that adds to the balance. Confirm |
| Loan in progress: current balance, reserve remaining, draws to date | For a depletion test | Plus the revised schedule |
Minimum viable: initial advance, holdback total, rate, interest method, and the month the loan is expected to pay off. Everything else can take a labelled default.
Step 2 — Explain the interest method in plain terms
Reading the full skill counts as a download. The contributor receives your name, company, and email.
Ratings & reviews
No written reviews yet. If you run this on a live file, say how it went. The next lender reading this page is deciding whether to trust it.
Examination record
Run it in Claude
- Copy the install command above
- Paste it into Claude, ChatGPT or Cursor
- It writes the skill in, fills in your firm’s details, and test-runs it with you
Prefer the file? The prompt above is for a package you already downloaded.
Details
More from The Helvetica Group
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