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Base Year Stop Calculator
Base year leases pass through only the expense increase above the first-year level. If there's a cap on opex growth (annual or cumulative), the tenant is further protected. This calculator runs the billing both ways — with and without cap — so both sides see what the cap is really worth.
Tenant billing (uncapped)
$18,000
Tenant billing (capped)
$6,336
Tenant savings from cap
$11,664
Opex gap above base year / SF
$2.25
Capped base year equiv / SF
$10.71
Expense growth vs base
24.3%
How the math works
In a base year lease the tenant pays their pro-rata share of opex over the base year level. A cap (e.g., 5% annual) protects the tenant by capping how fast the base year reference grows — above the cap, the landlord eats the overage.
Caps can be annual or cumulative. Cumulative caps are tenant-friendly: they lock in a compounding ceiling. Annual caps reset each year and leak more expenses to tenants over long leases.
How to Use
- Enter base year opex per SF and current year opex per SF.
- Enter tenant leased SF.
- Enter the annual opex cap percentage.
- Enter years since base year.
- Read billings with and without cap.
Frequently Asked Questions
Why gross up expenses?
When building occupancy is low, landlords gross up variable expenses (utilities, cleaning) to what they'd be at 95%+ occupancy. Otherwise the base year reflects a partially-occupied building, and tenants end up paying increases as lease-up happens.
Cumulative vs annual cap?
Cumulative: 5%/year compounding. Year 5 = 1.05^4 = 21.6% over base. Annual (with reset): each year capped at 5% over PRIOR year's actual — effectively uncapped if expenses grow faster than cap after a down year.
What's excluded from opex?
Typical exclusions: capital expenditures (unless amortized), debt service, financing costs, leasing commissions, tenant improvements, executive salaries, owner legal fees. Check the lease definition carefully.
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