Try it yourself
This is a real, working CalcForms calculator, right here on the page. Enter your details and watch the estimate update on the spot. It is exactly what your customers would use, and every submission lands in your dashboard as a lead.
What it calculates
- Shows live monthly cash flow, cap rate and cash-on-cash return as the investor enters rent and expenses
- Keeps your real multi-tab underwriting workbook: payment math on the mortgage, NOI rollup and vacancy and expense ratios
- Captures each investor as a lead with the full deal, purchase price and projected return already calculated
- Update rent assumptions, expense ratios or loan terms later just by asking ChatGPT
- Backtest against properties you already own so projected returns match your actual operating numbers
Why it closes more deals
A live number closes deals
Customers who see a real estimate the second they enter their details are far likelier to book than ones told to call for a quote. The number is the hook.
Runs your most complex spreadsheet
Multi-tab workbooks, lookup tables, tiered rates, conditional line items, the lot. If the math runs in Excel, CalcForms runs it behind a clean form.
Update it by chatting
Prices move. Ask ChatGPT to change a rate, add an option, or insert a step and the live form updates in seconds. No developer, no redeploy.
Backtest before you publish
Run your last 20 real jobs through it and tune the formula until the live estimate matches what you actually charge. Ship it once it lines up.
Why calculator forms convert — by the numbers
47.3% vs 2.8%
In an analysis of 50,000+ forms, interactive forms averaged a 47.3% conversion rate versus 2.8% for static forms. (Outgrow)
2× conversions
Interactive content generates roughly twice as many conversions as static content. (Content Marketing Institute)
51% of buyers
51% of B2B software buyers now begin their research in an AI chatbot rather than a search engine. (G2, 2026)
1 in 3
A third of B2B buyers have chosen a vendor they had never heard of before, on an AI assistant's recommendation. (G2, 2026)
How this form was built
No template builder and no code. One message to ChatGPT with CalcForms added:
Build this exact form
CalcForms is an app you add to ChatGPT once. After that you build and edit forms just by chatting. Works in Claude too.
- Add CalcForms to ChatGPT. Open the CalcForms app page, click Add, and sign in with your email. One time, about 60 seconds. A free ChatGPT account works. (Using Claude? Setup here.)
- Say the words below. ChatGPT builds the form with your math inside and gives you a link.
- Share it, then change it by asking. Send the link to customers. Change a rate or add a question later just by asking.
Step-by-step: turn your spreadsheet into a form, add your price list, show customers one number. All guides →
"Build a rental property ROI calculator from my underwriting workbook. Use the NOI tab for income minus vacancy and operating expenses, run PMT for the mortgage from the Financing tab, then output monthly cash flow, cap rate and cash-on-cash return on total cash invested."
Example run: An investor enters a 275,000 dollar property, 25 percent down, 2,400 dollars rent and 650 dollars expenses at 7 percent. The form shows roughly 9.6 percent cash-on-cash and a 6.1 percent cap rate, then sends you the lead with the full underwrite.
How does it work? CalcForms is an official ChatGPT app. Once it is added, ChatGPT can build, publish and update real calculator forms for you, all from the chat window. Your customers never need ChatGPT; they just open a link.
What it works out
Net operating incomeCap rateCash-on-cash returnMonthly cash flow
FAQ
Does it calculate cap rate and cash-on-cash, not just cash flow?
Can it use my vacancy and expense ratios?
Can I adjust assumptions as the market shifts?
Build yours in the next 10 minutes.
Your first form is free. No credit card.
Add to ChatGPT, free →