Every calculation prints with a built-in PE stamp + signature block, ready for sealed submittals.
Every tool shows the formula being applied, names every variable, cites a source, and supports
both Imperial and SI units. Organized by PE discipline. No login, no paywall.
Built for working Professional Engineers, not for FE prep.
Hydraulics & Water Resources
Manning's Equation
Open-channel flow: Q from n, A, Rh, S
Darcy-Weisbach
Pipe head loss with Swamee-Jain f
Moody Diagram
Friction factor: Colebrook, Swamee-Jain, Haaland
Hazen-Williams
Water-distribution head loss
Water Hammer
Joukowsky surge pressure and 2L/a closure time
Darcy's Law
Groundwater flow Q = KiA, seepage velocity
Reynolds Number
Flow regime: laminar / transitional / turbulent
Sharp-Crested Weir
Q = C · L · H3/2
Broad-Crested Weir
Spillway / overflow
V-Notch Weir
Triangular weir, low-flow measurement
Parshall Flume
Q = C · Han, 1 in to 50 ft
Theis Well Drawdown
Theis + Cooper-Jacob drawdown
Gradually Varied Flow
Direct step backwater / drawdown profile
Tank Drain Time
Torricelli time to empty a tank
Venturi Meter
Q from differential head or manometer
Orifice Flow
Q = Cd · A · √(2gh)
Time of Concentration
Kirpich + NRCS lag
Rational Method
Peak runoff: Q = CIA
NRCS Curve Number
SCS / TR-55 runoff depth and volume
Culvert Hydraulics
FHWA HDS-5 inlet + outlet control
Bridge Scour
HEC-18 contraction, pier & abutment scour
Linear Interpolator
Two-point + table; lin/log; inverse
Reservoir Routing
Modified Puls / Storage-Indication level-pool routing
Ogee Spillway
Q = C·L·He3/2, USACE EM 1110-2-1603
Drop Spillway
NRCS NEH-11 straight-drop principal spillway
Stepped Spillway
Energy dissipation, Chanson skimming-flow regime
Hydraulic Jump & Stilling Basin
Conjugate depth + USBR Type II/III/IV
Embankment Seepage
Casagrande phreatic line + Darcy seepage Q
Filter Criteria
Sherard / NRCS D15/D85 ratios
Riprap Sizing
USACE EM 1110-2-1601 D30; Isbash D50
Wave Runup & Freeboard
Wind setup + significant wave + Saville runup
Gravity Dam Stability
FoS overturning, sliding, base pressure with uplift
Dam Breach Peak Discharge
Froehlich 2008 + Xu-Zhang + MacDonald
Hazard Classification
FEMA P-94 low / significant / high screener
Inflow Design Flood (IDF)
% PMF by hazard class — FERC, FEMA, USACE
Environmental Engineering
BOD Removal
First-order kinetics, CSTR/PFR
MLSS & F:M Ratio
Activated sludge loading and SRT
Aeration Tank Sizing
Activated-sludge basin volume
Oxygen Transfer
SOTR ↔ AOTR with α, β, F
Settling Velocity
Stokes / transition / Newton regimes
Chlorine CT Disinfection
EPA SWTR Giardia / virus log inactivation
Lift Station Sizing
Wet well volume + cycle time
Hydraulic Detention Time
HRT and clarifier OFR
Geotechnical Engineering
Terzaghi Bearing Capacity
Strip / square / circular footing
Soil Classification (USCS + AASHTO)
Gradation + Atterberg limits → USCS symbol & group name, AASHTO group index, plasticity chart
Lateral Earth Pressure
Rankine Ka, K0, Kp
Slope Stability FoS
Infinite slope, c-φ, with seepage
Consolidation Settlement
1-D primary settlement, NC + OC paths
Pile Capacity
α/β methods, axial single pile
Permeability Test
Constant / falling head k, corrected to 20 °C
Cantilever Retaining Wall Design
Stability + ACI 318 stem, heel & toe rebar
Segmental Block Retaining Wall
Modular block gravity wall, max unreinforced height
Geogrid Retaining Wall
Reinforced block wall: layers, LTDS, pullout, length
Retaining Wall Block Calculator
Blocks, caps, gravel tons, geogrid rolls, cost
Soil Nail Wall
FHWA GEC 7 wedge stability, bond strength, nail length
Boussinesq Stress Distribution
Point, strip, rectangle (Newmark), circle — vs 2:1
Beam Deflection
SS & cantilever, point + UDL
Continuous Beam
1–5 spans, pattern live load, moment envelope
Truss Calculator
Roof & bridge trusses, NDS / AISC checks
3D Frame Analysis
Frames & buildings, diagrams, P-Δ, modal
Euler Buckling
Column Pcr, end conditions
Section Properties
A, I, S, r, Z — common shapes
AISC Allowable Stress
ASD tension, compression, flexure
AISC LRFD Steel Design
Design strength φPn — tension, compression, flexure
RC Beam Flexure
ACI 318 Whitney block, φMn
Neutral Axis (Built-Up & Composite)
ENA, PNA, I, S, Z — transformed sections
RC Beam Design (ACI 318-19)
Rebar, stirrups, T-beams, doubly reinforced, cracked section
RC Column Interaction Diagram
P–M diagram, tied/spiral, rect/circular, ties & slenderness
Transportation Engineering
Stopping Sight Distance
AASHTO SSD with grade correction
Vertical Curve
Crest & sag K-factor, low/high point
Horizontal Curve
R, D, T, L, M, E geometry
Superelevation
AASHTO e + f, min radius
Stopbar
Draw a road grid. Signals, stops, and roundabouts
Traffic Flow (Greenshields)
Capacity, q = kv, PHF, DHV, space-mean speed
Signal Timing
Yellow, all-red, ped, Webster cycle & splits
Crash Rate
Per MEV & 100 MVMT, critical rate
Mechanical / HVAC Engineering
Pump BHP
Hydraulic, brake, motor power
NPSH Calculator
NPSH available vs required: elevation, temperature, suction lift, margin check
Fan Affinity Laws
Speed / diameter / density scaling
Duct Pressure Loss
Round / rectangular, Darcy-Weisbach
Heat Exchanger LMTD
Counterflow, parallel, F factor
Psychrometric Load
Sensible & latent HVAC loads
Electrical Engineering
Voltage Drop
NEC AC voltage drop, Cu and Al
Three-Phase Power
kW, kVA, kVAR, PF correction
Motor FLA
Full-load amps, NEC 430.250
Transformer Sizing
kVA from connected load + DF
NEC Conduit Fill
Chapter 9 Tables 1, 4, 5
Chemical & Thermo Engineering
Ideal Gas Law
PV = nRT, with Z-factor
Antoine Vapor Pressure
P_sat from T, common compounds
CSTR / PFR Sizing
Reactor volume, 1st & 2nd order
Carnot & Refrigeration COP
Power cycle & refrigeration efficiency
Field / Astronomy
Sun Position & Solar Irradiance
Live sun path, elevation/azimuth (NREL SPA), clear-sky W/m², fixed vs tracking panels, shadows
Eclipse Predictor
Every solar eclipse 1900–2200 on a 3D globe: paths, contact times, totality duration
Eclipse Sun Position
Sun alt/az + path-of-totality check for photographers (Aug 2026 default)
Tsiolkovsky Rocket Equation
Δv from Isp and mass ratio, propellant for a target Δv, TWR, burn time
In Development
Long-form design walkthroughs that thread multiple PE-Calc tools end-to-end on real-world problems.
Browse all worked examples →
Separate from the free browser calculators above: downloadable macro kits for your CAD station,
built from the same production tooling. Plain source you can read and modify — no DLLs.
Most existing options bury the math behind ads, leave you guessing what coefficients they're using,
or were built for an undergraduate thermodynamics class twenty years ago and never updated.
Every PE-Calc tool shows the formula, names every variable, cites a reference, and lets you
hand-check the result. The calculators run entirely in your browser — nothing leaves your machine.
Both Imperial and SI units on every relevant tool, because real engineering happens in both.
Every tool's print layout includes a designated PE stamp area, signature line, license number, state, date,
and project / sheet field — formatted to slot into a sealed engineering submittal. Hit "Print with PE stamp box"
on any tool and you get a clean letter-size calculation sheet with the math, the inputs, the result, the cited
reference, and a stamp block ready for your seal and signature. Other calculator sites print a screenshot of an ad-cluttered
web page; PE-Calc prints engineering documentation.
A calculator that is quietly wrong is worse than none. The calculators’ formulas have been audited against the
references they cite, and an automated test suite runs the calculators’ own code against independently
computed answers on every change to the site. When a reader or an audit finds an error, the fix ships with a
new test so the same mistake cannot return. Reference cards state the edition and table they come from, such as
FHWA HDS-5 Table 12 or IBC Table 1806.2, and many include a worked example you can reproduce with a
calculator and the equations on the page. If you find a result you disagree with, the
contact page explains what to send.
New tools are added every week. The disciplines marked "in development" above will populate over
coming months. Have a calculator you'd like to see prioritized? Send a request through the
contact page or reply to any newsletter issue.