Impact Fee Calculator Formula

Understand the math behind the impact fee calculator. Each variable explained with a worked example.

Use the Impact Fee Calculator

Formulas Used

Total Impact Fee Per Unit

per_unit = fee_per_unit

Total Impact Fees (all units)

total_all_units = total_fees

Total School Fees

school_total = school_fee * num_units

Total Transportation Fees

transport_total = transportation_fee * num_units

Total Water & Sewer Fees

water_total = water_sewer_fee * num_units

Total Parks, Fire, Police & Other

parks_fire_other = (park_fee + fire_police_fee + other_fees) * num_units

Variables

VariableDescriptionDefault
num_unitsNumber of Units / Homes25
school_feeSchool Impact Fee Per Unit(USD)4500
transportation_feeTransportation Fee Per Unit(USD)3200
park_feeParks & Recreation Fee Per Unit(USD)2000
water_sewer_feeWater & Sewer Fee Per Unit(USD)5500
fire_police_feeFire & Police Fee Per Unit(USD)1200
other_feesOther Fees Per Unit(USD)800
fee_per_unitDerived value= school_fee + transportation_fee + park_fee + water_sewer_fee + fire_police_fee + other_feescalculated
total_feesDerived value= fee_per_unit * num_unitscalculated

How It Works

Impact Fees in Real Estate Development

Impact fees are one-time charges assessed by local governments on new development to help pay for the public infrastructure and services needed to serve the new residents.

Common Impact Fee Categories

  • Schools: Covers new classroom construction ($2,000-$10,000+ per unit)
  • Transportation: Road widening, traffic signals, transit ($1,500-$8,000 per unit)
  • Water & sewer: Treatment plant capacity, distribution lines ($3,000-$10,000 per unit)
  • Parks & recreation: New parks and facilities ($1,000-$5,000 per unit)
  • Fire & police: Station construction and equipment ($500-$3,000 per unit)

    • Impact on Development Feasibility

    Impact fees can total $10,000-$30,000 or more per unit, significantly affecting project feasibility. They are typically paid at the time of building permit issuance.

    Geographic Variation

    Impact fees vary enormously by jurisdiction. Some states limit or prohibit them, while others (like Florida, California, and Texas) have fees that can exceed $30,000 per unit in high-growth areas.

    Worked Example

    25-unit development with $4,500 school, $3,200 transportation, $2,000 parks, $5,500 water/sewer, $1,200 fire/police, and $800 other fees per unit.

    num_units = 25school_fee = 4500transportation_fee = 3200park_fee = 2000water_sewer_fee = 5500fire_police_fee = 1200other_fees = 800
    1. 01Fee per unit: $4,500 + $3,200 + $2,000 + $5,500 + $1,200 + $800 = $17,200
    2. 02Total for 25 units: $17,200 x 25 = $430,000
    3. 03School fees total: $4,500 x 25 = $112,500
    4. 04Transportation total: $3,200 x 25 = $80,000
    5. 05Water & sewer total: $5,500 x 25 = $137,500

    Ready to run the numbers?

    Open Impact Fee Calculator