Drainage Structure Calculators
Design inlets, culverts, weirs, outlets, and bridge scour countermeasures using FHWA HEC-22, HEC-18, HEC-14, and related methods.
Storm Drain Inlets
Design inlets for roadway and site drainage collection
Catch Basin Sizing
Size storm drainage inlets for roadway and parking lot applications
Inlet Interception
Calculate inlet efficiency and interception capacity using HEC-22 methods
Gutter Flow
Calculate gutter capacity, spread width, and flow velocity for inlet spacing
Roadway Gutter Calculator
Analyze uniform and composite roadway gutter sections and spread
Median/Ditch Drop-Inlet Calculator
Analyze median and roadside ditch drop inlets on grade or in sag
Horizontal Grade Inlet Calculator
Size inlet perimeter and spacing for zero- and near-zero-grade pavements
Building Drainage
Size roof drains and downspouts for building drainage
Subsurface Drainage
Design French drains and foundation drainage systems
French Drain Sizing
Size subsurface drainage systems including pipe and aggregate
Foundation Drain Design
Design foundation drainage systems for basement waterproofing
Trench Drain Capacity
Calculate linear trench drain capacity and sizing
Area Drain Spacing
Optimize area drain spacing for site drainage grading
Culvert Hydraulics
Analyze culvert inlet and outlet control conditions
Culvert Outlet Control
Calculate outlet control headwater using energy equation
Tailwater Analysis
Calculate tailwater depth at culvert and pipe outlets
Culvert Assessment Calculator
Screen culvert condition and prioritize maintenance, repair, or replacement
Bridge Hydraulics
Assess bridge scour and hydraulic vulnerability
Outlet Structures
Design outlet protection and energy dissipation
Outlet Protection Design
Design riprap aprons for outlet scour protection per HEC-14
Outlet Velocity Assessment
Assess erosion potential and permissible velocities at outlets
Energy Dissipator Design
Design stilling basins, impact basins, and drop structures
Weir Calculator
Calculate discharge or head for regular, V-notch, and irregular weirs
Pumping
Size pumps and sumps for drainage applications
Learning Resources
Understand the theory behind the calculations
HEC-22 Inlet Design Reference
Understanding inlet types and interception efficiency
Learn more: HEC-22 Inlet Design ReferenceOpen Channel Hydraulics
Inlet vs outlet control and headwater calculations
Learn more: Open Channel HydraulicsChannel Design Guide
Riprap sizing and scour prevention techniques
Learn more: Channel Design GuideLooking for a different type of calculator?
Browse All Calculators