How we calculate
Every BidFlow calculator combines four layers of information so the number you see is more than just math.
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1
The math
Standard quantity-takeoff formulas (area × thickness × waste factor, etc.) - the same logic any estimator would use in a spreadsheet.
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2
Public reference data
- BLS Producer Price Index - material prices, refreshed daily
- BLS Occupational Employment Statistics - regional labor rates, refreshed quarterly
- RSMeans City Cost Index - regional cost multipliers
- Published city permit fee schedules - weekly scrape on verified metros, state-level average for the rest
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3
Recent project medians
Anonymous results submitted by calculator users in your area, aggregated into a median and interquartile range. We store only the first three digits of your zip code, the project category, and the number - no names, emails, or addresses on anonymous submissions.
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4
Outlier detection
Every submission runs through per-category sanity bounds and compares against the regional median. Values more than three standard deviations from the median are automatically flagged and held for review - they don't move the median until a moderator approves or rejects them.
FAQs
How recent is "recent"?
Medians use a rolling 90-day window. Every result shows a "last verified" timestamp so you can judge freshness yourself.
What if there's not enough data for my zip?
We fall back in order: zip3 → metro area → state → national. The result tells you which level we used and the sample count behind the median.
What about permit fees specifically?
Every permit city page starts with a state-level average. When enough contractors submit real fees for a given zip, that city page upgrades from "state estimate" to "verified" and displays the real median with sample size.
Can I see the code?
Not yet open-source, but the category taxonomy, sanity bounds, and outlier thresholds are all documented in our estimating software guide.
Disclaimer
Every calculator result is a planning estimate, not a contractor quote. Always verify pricing with local contractors and your local permitting authority before making decisions.