About PE-Calc
Built by a licensed Professional Engineer for working engineers, students, and contractors.
Why this site exists
The two big incumbents — Engineering Toolbox and LMNO Engineering — are great resources but show their age. Layouts are dated, ads are aggressive, and many calculators don't show the formula they apply or the coefficient values they assume. PE-Calc fixes those three things in every tool.
Design rules every tool follows
- Show the formula. Each calculator displays the equation it's solving and names every variable. No black boxes.
- Spell out coefficients. Manning's roughness, weir discharge coefficient, friction factor — these aren't constants. Every tool either accepts the coefficient as input or shows the value being assumed.
- Cite a reference. Engineering calculators get re-derived in textbooks every few years. Each tool cites the source equation (Chow, Brater & King, ASCE manual, etc.) so you can chase it back.
- Run client-side only. Inputs and results stay in your browser. Nothing is sent to a server.
Author
PE-Calc is built and maintained by Michael Flynn, PE, a licensed professional engineer based in the southeastern US. Day job is dam engineering and stormwater design. PE-Calc grew out of internal tools used on real projects and is being released for free, supported by ads.
The dam safety work on this site is the part closest to the day job: the state-by-state dam safety section covers hazard classification, permit and exemption thresholds, and emergency action plan obligations, read from each state's own statute and administrative code rather than from a secondary compilation. North Carolina, South Carolina, Georgia and Virginia are written up in full and carry a last-verified date; the remaining states carry inventory data and a citation rather than a summary of requirements, because a stale paraphrase of a dam safety statute is worse than none.
Open-source work by the same author — including the free HydroCN curve-number plugin for QGIS — lives at github.com/mf4633.
The same toolbox includes downloadable CAD automation — the OpenRoads Field Kit (MicroStation VBA) and C3D Field Kit (AutoCAD Civil 3D LISP) — for drafters who want the same productivity at the CAD station.
Suggesting a tool
If there's a calculator you'd like to see prioritized, subscribe to the newsletter below and reply to any issue — tool requests are read and queued. The current backlog includes additional environmental, geotech, and structural calculators.