How our fee figures are made

When you drop a pin or search an address, we resolve the city, county, and state, then query our impact-fee database of researched fee schedules (currently strongest in Florida; single-family and multifamily residential have the broadest coverage, and commercial, industrial, and office schedules are sourced in a growing set of counties). Sourced fee lines link to the source document recorded for that specific fee. Results from this path are not estimates and carry no estimate banner.

If we have no sourced rows for a jurisdiction and project type, the calculator shows a modeled estimate, flagged with an amber “Illustrative estimate” banner. For each fee category the estimate is:

rate = national range point × state cost factor × population factor × county factor (categories limited to what state law allows)

• State authority filter. Not every state authorizes impact fees, so categories are filtered before anything is computed. In states with no impact-fee enabling act (e.g. Mississippi, Iowa, Michigan), only water & sewer utility connection/capacity charges are estimated — utility ratemaking authority exists everywhere, but the other impact-fee categories generally can't be levied there. In states whose statute bars specific categories, those are excluded (e.g. school impact fees in Idaho, Texas, Utah, and Wisconsin). In states where such charges exist only through home rule or special acts (e.g. Ohio, Tennessee), estimates carry an explicit caveat.
• National range point. Each development type × category has a national [min, max] range spanning roughly the 25th–75th percentile of jurisdictions that levy that fee (jurisdictions charging nothing are excluded). A deterministic hash of the jurisdiction name picks a stable point in the range, so the same place always gets the same numbers. Nonresidential water & sewer is the exception: it is modeled as a flat one-time connection & capacity charge (roughly a 1-inch meter), shared across commercial, industrial, and office, because utilities price those fees per meter size rather than per square foot.
• State cost factor. A per-state multiplier (1.00 = US median) reflecting construction-cost indices and observed fee levels — e.g. HI 1.95, CA 1.85, FL 1.25, GA 1.00, MS 0.75.
• Population factor. Real population from a bundled GeoNames/Census-derived dataset (places of 5,000+ residents): under 5k ×0.75, 5–25k ×0.90, 25–100k ×1.00, 100–500k ×1.20, over 500k ×1.40. Counties currently get no size adjustment (we don't bundle county populations yet).
• County factor. Each estimate covers exactly one jurisdiction: an incorporated city, or the unincorporated county when the location isn't inside a city — never both, so nothing is double-counted. The single estimate includes every fee category that applies at the location (including school-district and county-level fees inside city limits). County-level estimates are scaled ×0.40, reflecting that unincorporated areas typically levy far fewer and lower fees than incorporated cities.

The anchor is the most recent national impact-fee survey (published 2019), escalated roughly +10% — a deliberately conservative fraction of documented 2019–2024 construction-cost inflation (+17.3% in 2022, +6.5% in 2023, +3.4% in 2024 per industry cost indices) — and cross-checked against 2023–2026 adopted schedules as upper bounds, including:

• Austin Water capital recovery fees (effective Oct 2023)
• Fort Worth transportation impact fee study (2023)
• Fresno citywide fee schedule (effective Sept 2024)
• Boise FY2026 impact fee schedule
• Franklin, TN road impact fee (Ord. 2023-41)
• Orange County, FL residential impact fees (2024)
• California State Allocation Board Level 1 school fees (2024)
• Phoenix 2025 infrastructure financing plan; Utah League fee summaries (2024–25)

Ranges we could not re-verify with post-2022 sources (notably per-square-foot commercial, industrial, and office figures other than water & sewer, which jurisdictions rarely publish per sqft) are carried forward from the 2019 survey with the same conservative ~10% escalation and are marked as such in our internal citation table. Nonresidential water & sewer is instead modeled as a flat per-meter connection charge, cross-checked against 2023–2024 adopted schedules (Fresno, Austin).

• Estimates are not adopted fee schedules. Two similar towns can have very different actual fees — including zero. Always confirm with the jurisdiction before relying on any figure.
• Estimates are not yet calibrated against our own sourced database — that calibration is the top item on our roadmap.
• County estimates get no population-based size adjustment yet, and the bundled place populations are a few years old (they only need to place a city in a coarse size band).
• The national survey anchor is from 2019; the conservative ~10% escalation is an approximation (intentionally well below full documented inflation), not a re-survey.
• Estimate source links point to a search of the jurisdiction's municipal code, not to a specific ordinance.
• The state authority classification is our editorial reading of enabling statutes and leading cases, not legal advice; home-rule and special-act coverage varies within states, so a state-level classification is necessarily coarse.

Sourced results show per-fee line items with “Source” links to recorded documents. Estimates show an amber banner, an “(illustrative)” total, and an expandable “How this estimate was made” panel listing the exact adjustments applied to that jurisdiction — including its population band and state factor.

Seeing an estimate where you need sourced numbers? Use the “Request sourced fees” form on the calculator and we'll prioritize that jurisdiction and email you when it's ready.