A free calculator and a library of guides from a developer who runs these numbers for a living — not a content mill.
Enter the basics of your deal. You'll get your yield on cost and an instant go / walk read — the same first screen a developer runs before spending a dollar on architecture.
The full chain — gross area, efficiency, rentable feet, rents, lease-up, OpEx, NOI, yield on cost, and the development spread that decides build-or-walk. With a real deal that didn't pencil.
The two yields that decide every deal, current 2025–26 cap rates by class, and the rate-expansion risk that quietly kills deals.
A pro forma is a story about time. Sources and uses, the lease-up J-curve, the interest reserve, and the returns the timeline pays out.
Drive-up vs. climate, shell vs. all-in, the 2025–26 cost drivers most guides miss — and how to turn $/sf into a verdict.
Absorption benchmarks, why stabilization now runs ~36 months, and the reserve mistake that ends good projects.
Small units rent for double the $/sf of large ones. Your mix sets the blended rate — one average number misprices the deal.
What's in one, what it costs, the supply test that decides saturation, and how to read it without being fooled.
I'm Jacob Magna — a ground-up real estate developer and software founder. I underwrite self-storage and mixed-use deals for a living, and I build the software behind the businesses I work with: I founded Magna Software LLC, which builds custom operating platforms for owner-run companies, and I'm co-founder of DocInsured, a certificate-of-insurance compliance platform. Storage Underwriter is where those two sides meet — I built the same institutional-grade model I run my own deals through, and the reasoning behind it, for first-time developers walking into a hot, unforgiving asset class. Every guide here is grounded in current data and a real deal, including one of mine that didn't pencil.