Why It Matters
You need PGI because every other income figure in your deal analysis flows from it. Effective Gross Income starts with PGI minus vacancy. Annual rental income on a stabilized property approaches PGI — but never quite reaches it.
Here's how to calculate it:
PGI = Market Rent per Unit × Number of Units × 12 + Other Income
On a 4-unit property where each unit rents for $1,400/month, PGI is $1,400 × 4 × 12 = $67,200. Add $1,800/year in laundry and parking revenue and PGI is $69,000. That's the maximum the property can produce. Real income will be lower — but without knowing the ceiling, you have no frame for evaluating whether your actual revenue is good or bad.
PGI also powers the break-even point calculation and feeds directly into underwriting tools that project the holding period return over a multi-year hold. Learn to use it precisely, and deal analysis becomes a lot less guesswork.
At a Glance
- Formula: PGI = Market Rent per Unit × Number of Units × 12 + Other Income
- What it measures: Maximum theoretical annual revenue at 100% occupancy and full market rent
- Includes: Base rents + ancillary income (laundry, parking, storage, pet fees)
- Does not include: Vacancy deductions, credit loss, operating expenses
- Next step in waterfall: PGI − Vacancy & Credit Loss = Effective Gross Income (EGI)
- Used in: Pro forma underwriting, valuation, income capitalization, break-even point analysis
PGI = Market Rent per Unit × Number of Units × 12 + Other Income
How It Works
Starting with market rent. PGI uses market rent — not what current tenants pay. If a tenant has been in place for six years and pays $950 on a unit that now rents for $1,250, your PGI reflects $1,250. This matters for value-add deals: current rent rolls understate PGI because below-market leases drag the number down. The gap between in-place rents and market rents is the upside.
Multiplying by units and months. The formula multiplies market rent by the number of units and by 12 to annualize. On a 10-unit building at $1,100/month per unit, that's $132,000. Every unit at every month — the ceiling, not the expectation.
Adding ancillary income. PGI captures all revenue streams the property could generate: laundry machines, covered parking, storage units, pet fees, and late fees. Some underwriters exclude late fees (not a dependable income source) and utility bill-back income (a passthrough rather than true revenue). Be consistent — whatever you include in PGI for one property, include for all comparable properties so your analysis stays apples-to-apples.
The waterfall from PGI to NOI. PGI sits at the top of the income waterfall. Subtract a vacancy and credit loss allowance (typically 5–10% of PGI for stabilized multifamily) to get Effective Gross Income (EGI). Subtract operating expenses from EGI to reach NOI. The annual rental income a property actually collects in a given year will fall somewhere between PGI and EGI — PGI sets the benchmark against which you measure that performance.
Real-World Example
Raj is analyzing a 6-unit apartment building in Phoenix. Current leases are running below market — tenants have been there for years and rents haven't been adjusted. Here's how he builds PGI:
- 6 units at current rents: $950 × 6 = $5,700/month → $68,400/year in current gross rent
- 6 units at market rents: $1,175 × 6 = $7,050/month → $84,600/year at market
- Covered parking: 4 spots × $75/month = $300/month → $3,600/year
- Storage lockers: 3 lockers × $40/month = $120/month → $1,440/year
PGI at current rents + ancillary: $68,400 + $3,600 + $1,440 = $73,440
PGI at market rents + ancillary: $84,600 + $3,600 + $1,440 = $89,640
The seller is marketing the property on current income. But Raj's PGI analysis shows there's $16,200/year of revenue upside once leases are renewed at market. Using a 6.5% cap rate, that revenue gap adds roughly $249,230 to the stabilized value — far more than any purchase price discount the seller is offering.
Raj also uses PGI to check the break-even point. With $58,000 in annual operating expenses and debt service, he needs $58,000 / $89,640 = 64.7% occupancy to break even. Six units means he can afford to have two units vacant and still cover his obligations. That margin gives him confidence in the deal's downside.
Pros & Cons
- Sets the analytical ceiling — Every income and cash flow figure is evaluated relative to PGI, giving you a consistent benchmark for the property's true earning potential
- Surfaces value-add opportunity — The gap between in-place PGI (current rents) and market PGI reveals hidden upside invisible on current rent rolls
- Feeds the entire underwriting waterfall — EGI, NOI, cap rate, and holding period return all trace back to a well-defined PGI
- Enables apples-to-apples comparison — Using market rent for PGI lets you compare properties regardless of their current lease terms or occupancy status
- Anchors the break-even calculation — Dividing fixed obligations by PGI gives you a maximum vacancy the deal can absorb before it stops covering its costs
- 100% occupancy is theoretical — PGI assumes full occupancy and full-price rent, conditions that never exist in the real world and that you should never expect to collect
- Market rent requires verification — Using stale or inflated market rent comparables overstates PGI and makes a deal look better than it is; garbage in, garbage out
- Excludes vacancy by design — Investors who confuse PGI with actual expected income consistently underestimate the income haircut that vacancy and credit loss will impose
- Ancillary income is often overstated — Pet fees, parking, and laundry revenue in pro formas frequently include aspirational items that don't currently exist, inflating PGI
- Doesn't capture expense reality — A high PGI means nothing if operating costs are also high; PGI must be read in context with expense ratios, not in isolation
Watch Out
- Current rent vs. market rent confusion. Many sellers and brokers present current gross rent as if it were PGI. If leases are below market, the number being quoted is understated PGI — not a reason to pay more, but a signal to underwrite the actual market rent ceiling and verify the path to getting there.
- Ancillary income without supporting evidence. A pro forma that lists $8,000/year in parking income but shows no current parking contracts is projecting PGI from hope, not data. Require actual revenue documentation for every ancillary income line item before it enters your PGI figure.
- Forgetting other income exists. If a property has coin-operated laundry, billboards, cell tower leases, or storage units, failing to include them understates PGI. Run a complete inventory of every revenue-generating feature before you finalize the number.
- Applying PGI as if it were expected income. PGI is the ceiling. Build your cash flow projections on Effective Gross Income — PGI minus a realistic vacancy factor — not PGI itself. A 5-unit property with $90,000 PGI and a 7% vacancy allowance generates $83,700 EGI, and that's the number your debt service needs to support.
- Ignoring the rent-vs-buy context. In markets where homeownership costs have risen sharply, rental demand is strong, which supports higher market rents. But in markets where renting and buying are close to parity, rent growth slows. Your PGI depends on where rents are headed, not just where they are today.
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The Takeaway
Potential Gross Income is the starting line of every rental property analysis — the maximum revenue the asset could generate under perfect conditions. It never actually happens: vacancy, credit loss, and below-market leases always pull actual income below PGI. But that gap is exactly where deal analysis lives. You need PGI to calculate EGI, to verify the break-even point, to size up value-add upside, and to track whether a stabilized property is performing close to its theoretical ceiling. Master the formula, use market rents (not in-place rents), and include every genuine ancillary income source — then remember to haircut it before you commit to any pro forma projection.