Line Sizing — Companion Article

1. What this tool does

Line sizing replaces the coming-soon Pipe Size Calculator and Max Flow Estimator with one page. It reports mean velocity, a candidate NPS list, or a maximum flow.

The page does not store a pipe dimension table. Inside diameter comes from the Engineering API when the row stores one: a stored inside diameter, or a stored outside diameter minus twice a stored wall thickness. If those facts are absent, the user enters a wall thickness or a bore. Outside diameter is filled from the catalogue when the row stores one, and the user can change it. Inside diameter is then outside diameter minus twice the wall thickness. A result that uses a typed wall or bore is marked user-entered. When the catalogue stores a wall or an inside diameter, that stored value is used.

2. When to use it

Use it when a designer has a flow, a velocity limit, or both, and wants mean velocity, a candidate NPS list, or a maximum flow.

Pipe Diameter on this site is a separate calculator. It does not call the Engineering API. This page does, for catalogue entities.

3. Inputs

1. Choose a mode: flow to velocity; flow and a velocity limit to a minimum NPS; or one size and a velocity limit to maximum flow.
2. Choose a schedule, and an NPS when the mode needs one size. The lists are canonical category Pipe with an inch nominal size and a non-blank schedule.
3. For one NPS, read the outside diameter. It is the catalogue value when the row stores one. The user can change it. If the row has no wall and no inside diameter, enter a wall thickness (mm or in) or a bore. If both are entered, the bore is used.
4. For a minimum NPS, enter one wall thickness for every candidate size that has no catalogue wall or inside diameter. On a row, an optional bore or wall replaces that assumption.
5. Enter the flow (m3/h, L/s, or US gpm) or the velocity limit (m/s or ft/s). The velocity limit is the user’s. The page does not print a typical velocity band.
6. For Reynolds number, enter density (kg/m3 or lb/ft3) and dynamic viscosity (Pa·s or cP). The page does not store a fluid table. There is no preset number.
7. API RP 14E coefficient C starts at 100. It is a user input.
8. Pressure drop per 100 m is off until the box is ticked. Roughness starts at 0.045 mm. It is a user input.

4. How it works

The running tool is the calculation. This section repeats the method already written for version 1.1.0. It does not add a pipe dimension table.

Mean velocity is volumetric flow divided by the internal area. Maximum flow is the velocity limit times that area.

Inside diameter is the stored inside diameter, or the stored outside diameter minus twice the stored wall, when those facts exist. Otherwise it is the outside diameter minus twice the wall the user enters, or the bore the user enters. A typed wall or bore is marked user-entered.

Unit factors match the PipingDesigners unit converter: 1 in = 0.0254 m, 1 ft = 0.3048 m, 1 US gallon = 0.003785411784 m3, 1 lb = 0.45359237 kg, 1 ft3 = 0.028316846592 m3, 1 cP = 0.001 Pa·s.

Reynolds number is density times velocity times inside diameter, divided by dynamic viscosity. Laminar is below 2300, transitional is 2300 to 4000, and turbulent is above 4000. Those are the conventional Moody-diagram bands. They are not a code limit and not an API fact.

API RP 14E erosional velocity is Ve = C / sqrt(rho), with rho in lb/ft3 and Ve in ft/s. The page converts density into lb/ft3 and reports Ve in ft/s and m/s. It does not switch C to a metric coefficient. The edition is not in this repository. C stays a user input. The starting value is 100.

Optional pressure drop uses the Darcy–Weisbach equation over 100 m, in pascals. The friction factor is the Swamee–Jain explicit approximation of Colebrook–White (Swamee and Jain, Journal of the Hydraulics Division, ASCE, 1976), used only for Reynolds number 5,000 to 100,000,000 and relative roughness 0.000001 to 0.01. It is not an iterated Colebrook solution. The roughness box starts at 0.045 mm, the rounded commercial-steel value 0.00015 ft. The Engineering API has no roughness fact.

5. Understanding the result

The page reports the result for the mode that was chosen: a velocity, a minimum NPS, or a maximum flow.

A row with neither a catalogue inside diameter nor a user wall or bore shows the missing-data note. A smaller size with no inside diameter blocks a minimum claim. A larger size is not highlighted in its place.

A result that uses a typed wall or bore is marked user-entered. It is not a catalogue result.

Reynolds number, erosional velocity, and pressure drop appear only from the inputs in section 3. Pressure drop outside the Swamee–Jain range is not calculated.

6. Engineering considerations

The velocity limit, density, viscosity, roughness, and C are user entries. The page does not print a typical velocity band and does not store a fluid table.

Confirm C against the edition in use. Confirm roughness against the roughness table in use.

Catalogue facts on this database are UNVALIDATED unless the API says otherwise.

This page is not the reserved 03 flow endpoint.

7. Example

Worked case is the data gap, not a velocity. Read on the Engineering API on 2026-10-02. It was not re-run for this remap.

Entity 43539, ASME NPS 2, schedule 40, ASTM A106:

• MATCHING_PIPE_OD 2.375, unit blank, nominal unit in
• SCHEDULE 40
• no WALL_THICKNESS
• no INSIDE_DIAMETER and no INTERNAL_DIAMETER

The page reports that the row stores an outside diameter and does not store wall thickness or inside diameter. It does not substitute a dimension table, and it does not print a velocity until a wall or a bore is entered. This article does not supply a wall thickness for the example. A velocity from a typed wall or bore is marked user-entered. It is not a catalogue result.

8. Standards/references (licensed vs interim)

Staging database on record: v2.5.3, 81,851 entities, 1,245,305 facts. Production database on record: v2.5.1, 81,851 entities, 1,234,262 facts. The Engineering API v2.5.1 contract stays frozen unless workstream 03 versions it. This page does not add an endpoint.

The method names already written for version 1.1.0 are the continuity relation for velocity and maximum flow, the conventional Moody-diagram bands, API RP 14E as cited with C left as a user input, and the Swamee–Jain 1976 approximation for the optional pressure drop. The API RP 14E edition is not in this repository. This draft does not class those sources as licensed or as interim. The interim pattern in the owner decisions log is ASME B36.10-2022 Table 2-1. This page does not store that table. Owner engineering review confirms the source classification before publish.

9. Limitations/disclaimer

• A catalogue row with no wall and no inside diameter produces no velocity until a wall or a bore is entered. That is the current ASME pipe record, including NPS 2 schedule 40. The typed value is marked user-entered.
• In the minimum-NPS mode, a smaller size with no inside diameter blocks a minimum claim. A larger size is not highlighted in its place.
• Supplier category PIPE and millimetre nominal sizes are not in the NPS list.
• Density, viscosity, roughness, C, and the velocity limit are user entries.
• Pressure drop outside the Swamee–Jain range is not calculated.
• This page is not the reserved 03 flow endpoint (tools register tool #6).
• The page at /tools-training/line-sizing/ is not recorded as created. The plugin does not create it.

A member check is not an engineering fact. The note is under Repository notes.

10. Use the tool

Calculate now: Line Sizing

The page is created in WP Admin if it does not exist. Title: Line Sizing. Slug: line-sizing. Parent: Tools and Training. Content:

Line sizing

Mode

Flow to velocity Flow and velocity limit to minimum NPS Size and velocity limit to maximum flow

Schedule NPS

Dimensions

Choose an NPS. Outside diameter is filled from the catalogue when the row stores one. You can change it.

Outside diameter — catalogue value, you can change it in mm Wall thickness mm in or bore / inside diameter in mm

Wall thickness for all candidate sizes mm in

Applied only to rows with no catalogue wall or inside diameter. A bore or wall typed on a row replaces it for that row. Catalogue wall and inside diameter are used when the API returns them.

Flow m3/h L/s US gpm Velocity limit m/s ft/s Density kg/m3 lb/ft3 Dynamic viscosity Pa·s cP API RP 14E coefficient C Pressure drop per 100 m Absolute roughness mm in Calculate

Sources

Inside diameter is the stored inside diameter, or the stored outside diameter minus twice the stored wall thickness, from the Engineering API. If those facts are absent, enter a wall thickness or a bore. The page computes inside diameter as outside diameter minus twice the wall thickness. It does not substitute a dimension table. A result that uses a wall or a bore you typed is marked as user-entered. When the catalogue later stores a wall or an inside diameter, that stored value is used and the typed wall or bore is not.

Mean velocity is volumetric flow divided by the internal area. Maximum flow is the velocity limit times that area. Unit factors match the PipingDesigners unit converter: 1 in = 0.0254 m, 1 ft = 0.3048 m, 1 US gallon = 0.003785411784 m3, 1 lb = 0.45359237 kg, 1 ft3 = 0.028316846592 m3, 1 cP = 0.001 Pa·s.

Reynolds number is density times velocity times inside diameter, divided by dynamic viscosity. Laminar is below 2300, transitional is 2300 to 4000, and turbulent is above 4000. Those are the conventional Moody-diagram bands, not a code limit and not an API fact.

API RP 14E erosional velocity is Ve = C / sqrt(rho), with rho in lb/ft3 and Ve in ft/s. C is a user input. The starting value is 100. Confirm C against the edition you use. This page converts density into lb/ft3 and reports Ve in ft/s and m/s. It does not switch C to a metric coefficient.

Density and viscosity are user entries. This page does not store a fluid table.

The velocity limit is user-entered. This page does not print a typical velocity band.

Optional pressure drop uses the Darcy–Weisbach equation over 100 m. The friction factor is the Swamee–Jain explicit approximation of Colebrook–White (Swamee and Jain, Journal of the Hydraulics Division, ASCE, 1976), used only for Reynolds number 5000 to 100,000,000 and relative roughness 0.000001 to 0.01. It is not an iterated Colebrook solution. The roughness box starts at 0.045 mm, the rounded commercial-steel value 0.00015 ft. It is a user input. The Engineering API has no roughness fact. Confirm it against the roughness table you use.

Catalogue facts are UNVALIDATED observations unless the API says otherwise.

. Version 1.1.0. Re-check this article when the tool version changes.

How this calculation works: companion path TBD.

That return link is not on the tool page. This draft does not add it. The public article path is TBD because this file is not published.

The article stays public if the tool is restricted. A visitor with no entitlement sees a lock message on the tool, not a bare “Access denied”. The copy is in the Companion Article standard. This draft does not place that lock on the page and does not mark the tool free, Pro, or Enterprise.

Related tools

Pipe Diameter, at /tools-training/pipe-diameter/, is a separate calculator. It does not call the Engineering API. This page does, for catalogue entities.

The coming-soon Pipe Size Calculator and Max Flow Estimator are the tiles this page replaces. They are not peer calculations in this article.