Калкулатор за Тръбно Сечение
Изчислете площта на вътрешния поток, площта на стената и обема на линеен метър по външен диаметър и дебелина на стената.
Circular Pipe Area Calculator
Inside Diameter (ID) will automatically be computed as: OD - (2 × t).
What Is Circular Pipe Area? Flow Lumen vs. Structural Wall Area
Every circular pipe, tubing, or conduit is fundamentally a hollow cylinder with two separate cross-sectional areas that serve entirely different physical roles in engineering.
Internal flow area (lumen area) is the hollow interior passage through which water, oil, or gas travels (A_flow = π·ID²/4). It dictates hydraulic capacity, volumetric flow rate, and pressure drop.
Pipe wall area is the annular ring of metal or plastic that contains internal pressure (A_wall = π/4·[OD² - ID²]). It determines pipe burst pressure rating, weight per foot, and material cost.
Pipe Geometric Dimensions & Flow Parameters
| Parameter | Formula | Example (2" Sch 40) | Engineering Application |
|---|---|---|---|
| Inside Diameter (ID) | ID = OD - (2 × t) | 2.067 in | Effective bore dimension |
| Internal Flow Area (A_flow) | A = (π × ID²) / 4 | 3.356 in² | Flow velocity & pump head |
| Wall Material Area (A_wall) | A = (π / 4)(OD² - ID²) | 1.075 in² | Pipe weight & burst pressure |
| Gallons Liquid / Linear Foot | Gal/ft = A_flow × 0.05195 | 0.174 gal/ft | Hydronic loop water volume |
| Steel Pipe Weight / Foot | Wt = A_wall × 3.40 lb/in² | 3.65 lb/ft | Pipe hanger support spacing |
4 Core Pipe Calculation Methods
Choose your method depending on whether you are sizing pump flow, checking pressure burst safety, or determining pipe hanger loads.
Direct Flow Lumen: A_flow = (π × ID²) / 4
The canonical hydraulic equation. Uses inside diameter ID directly to calculate the fluid channel cross-sectional area.
OD & Thickness: ID = OD - 2t
When you measure outer diameter with calipers and read wall thickness from piping specs: A_flow = [π × (OD - 2t)²] / 4.
Fluid Continuity Velocity: v = Q / A_flow
Determine fluid velocity to ensure water stays within ASHRAE standards (typically 4 to 8 ft/sec to prevent noise and erosion).
Barlow's Formula: P = (2 × S × t) / OD
Relates internal burst pressure P to material yield strength S, wall thickness t, and outside diameter OD.
Piping Physics: Flow Lumen & Annular Wall Math
Deriving pipe inside diameter, flow area, and volumetric capacity per foot:
Schedule 40 vs. Schedule 80 Standard Pipe Sizing Table
Comparison of outside diameter, wall thickness, inside diameter, flow area, and gallon capacity per linear foot.
| NPS Size | Actual OD | Sch 40 ID | Sch 40 Flow Area | Sch 80 ID | Sch 80 Flow Area | Sch 40 Gal/Ft |
|---|---|---|---|---|---|---|
| 1/2" | 0.840 in | 0.622 in | 0.304 in² | 0.546 in | 0.234 in² | 0.0158 |
| 3/4" | 1.050 in | 0.824 in | 0.533 in² | 0.742 in | 0.432 in² | 0.0277 |
| 1" | 1.315 in | 1.049 in | 0.864 in² | 0.957 in | 0.719 in² | 0.0449 |
| 2" | 2.375 in | 2.067 in | 3.356 in² | 1.939 in | 2.953 in² | 0.1743 |
| 3" | 3.500 in | 3.068 in | 7.393 in² | 2.900 in | 6.605 in² | 0.3840 |
| 4" | 4.500 in | 4.026 in | 12.730 in² | 3.826 in | 11.497 in² | 0.6613 |
4 Detailed Solved Real-World Examples
Realistic engineering problems spanning plumbing flow, drainage slope, HVAC volume, and pipe weight.
3/4-Inch Type L Copper Pipe Water Velocity
A domestic shower line carries 5 gallons per minute (GPM) through a 3/4" Type L copper pipe (ID = 0.785 in):
Chilled Water Closed Loop System Volume
Calculate total water holding capacity for 500 feet of 4-inch Schedule 40 steel pipe:
Empty Weight of 6-Inch Schedule 80 Steel Pipe
Find the dead load steel weight of a 100-foot run of 6" Sch 80 pipe (OD = 6.625", wall t = 0.432"):
24-Inch Reinforced Concrete Pipe (RCP) Full Flow
Calculate full-flow cross-section for a 24-inch interior diameter stormwater pipe:
Common Pitfalls in Circular Pipe Area Calculations
Wrong: ID = OD - t. Correct: ID = OD - 2t. Because pipe diameter spans across the pipe, it crosses the wall on both sides.
A 2-inch pipe does NOT have a 2.000" inside diameter. A 2" Sch 40 pipe has ID = 2.067". Always check schedule tables.
Multiply your pipe's inside flow area in square inches by 0.05195 to immediately obtain the fluid volume in US Gallons per foot.
Stepping up one pipe size (e.g. from 1/2" to 3/4") increases flow area by 75%, allowing much higher flow with little pumping head.
Industry Applications of Circular Pipe Calculations
Commercial Plumbing
Sizing main domestic cold and hot water headers using fixture unit (WSFU) flow demand tables.
HVAC Hydronic Loops
Calculating glycol-water expansion tank volume and circulating pump head friction loss.
Fire Sprinkler Engineering
Hydraulic density discharge (NFPA 13) calculations through Schedule 10 and 40 branch lines.
Municipal Storm Drainage
Civil storm sewer sizing using Manning's equation for circular concrete culverts under gravity flow.
Oil & Petrochemical Lines
API 5L transmission line sizing, crude oil transport velocity, and high-pressure surge containment.
Industrial Chemical Dosing
Determining chemical residence time and Reynolds numbers in PTFE and PVDF process piping.
Често задавани въпроси: Тръбно сечение
Отговори на най-важните въпроси за формулите, радиуса, диаметъра и мерните единици
Как се изчислява вътрешният диаметър (ID)?
Вътрешен диаметър ID = Външен диаметър OD - (2 × Дебелина на стената).
Специализирани калкулатори за кръг
Изберете инструмент за изчисление според вашите геометрични параметри
Area of Circle Calculator
Find circle area from radius, diameter, or circumference with instant formulas.
Калкулатор за Лице на Кръг по Диаметър
Calculate circle area directly from diameter using A = (πd²)/4.
Калкулатор за Лице на Кръг по Обиколка
Determine circle area directly from perimeter using A = C²/(4π).
Калкулатор за Лице на Полукръг
Semicircle area, curved arc length, and total perimeter with flat base.
Калкулатор за Сектор и Сегмент на Кръг
Circular sector and segment area from radius and central angle.
Калкулатор за Лице на Кръгов Пръстен
Annulus, washer, and circular ring surface area between concentric circles.
Калкулатор за Напречно Сечение на Кръг
Engineering cross-section for circular shafts, rebar, cables & tensile stress.
Лице на Кръг чрез Интегриране
Calculus derivation of circle area with polar, Cartesian, and shell integrals.