Engineering reference cards
Single-page printable cheat sheets for the values engineers look up over and over — roughness coefficients, discharge coefficients, curve numbers, loss factors, and more. Every card names the source equation and cites a reference, and prints clean on one letter page. No login, no paywall.
Manning's n
Roughness coefficient — concrete to natural streams to floodplains
Hazen-Williams C
Pipe roughness for water mains — new vs. aged values
Runoff Coefficients (C)
Rational Method C by land use, surface, slope, frequency
Curve Numbers (CN)
NRCS / TR-55 CN by land use & hydrologic soil group, with HSG & ARC
Weir Coefficients (Cd)
Sharp-crested, broad-crested, V-notch, ogee, Cipolletti
Tc Methods Compared
Kirpich vs. NRCS Lag vs. TR-55 segmental vs. FAA
Minor Loss Coefficients (K)
Fittings, valves, bends, entrances & exits — h = K·V²/2g
Pipe Roughness (ε)
Absolute roughness by material for Darcy-Weisbach / Moody
Culvert Entrance Loss (Ke)
HDS-5 inlet coefficients — concrete pipe, CMP, box culvert
SCS Storm Distributions
Type I, IA, II, III 24-hr curves & where each applies
Open Channel Geometry
A, P, R, T formulas by shape + best hydraulic section
Orifice Coefficients (Cd)
Outlet & riser Cd — Q = Cd·A·√(2gh)
Hydraulic Jump
Froude, sequent depth, energy loss, jump types
Riprap Sizing
Isbash / HEC-11 D50, gradation, thickness, filter
Specific Energy & Critical Depth
E = y + V²/2g, critical depth, alternate depths
Storm Sewer Design Criteria
Velocity, slope, n, pipe size, cover, full-flow capacity
Stokes Settling Velocity
Particle settling, overflow rate, Type I settling
Reynolds Number Regimes
Laminar/turbulent thresholds + water viscosity
How these differ from the calculators
The calculators solve a specific equation for your inputs and print with a PE stamp block. These reference cards are the lookup tables behind them — the coefficient values, gradation limits, and design criteria you reach for first. Print one, tape it to the monitor, and skip digging through Chow or the TR-55 appendix every time. Each card cites where its values come from.