NFPA in USA

Engineering calculator

Fire Pump Horsepower Calculator

Calculate approximate pump horsepower from flow, head, specific gravity, and efficiency.

Fire PumpEngineeringWorkpaper

Calculation workpaper

Enter inputs, review outputs, then use the guidance below before carrying the result forward.

US customary units

Calculation inputs

Enter project screening values in the units shown.

Ready

Worksheet header

Optional project fields for keeping the calculation screen traceable.

Results

Ready

Pump horsepower

77.44 HP

Calculated output

Next standard motor size

100 HP

Calculated output

Pump efficiency

75 %

Calculated output

Pump horsepower77.44HP
Next standard motor size100HP
Pump efficiency75%

NFPA in USA calculation workpaper

Fire Pump Horsepower Calculator

Engineering ยท Fire Pump

nfpainusa.comGenerated record

Project record

Project ID
Not entered
Area
Not entered
System
Not entered
Revision
Not entered
Prepared by
Not entered
Checked by
Not entered

Inputs

Pump flow
1000 GPM
Total head
230 ft
Specific gravity
1
Pump efficiency
0.75

Results

Pump horsepower
77.44 HP
Next standard motor size
100 HP
Pump efficiency
75 %

Calculation basis

Formula
HP = Q x H x SG / (3960 x efficiency)
Reference standard
Engineering
Professional boundary
Verify adopted code, project criteria, listed equipment data, and AHJ requirements before relying on this record.
NFPA in USAnfpainusa.comThis is a calculation record, not a signed or sealed engineering document.

Calculation basis

Use the formula and linked reference data after the result is visible. Keep input selection separate from the calculation screen.

Formula

HP = Q x H x SG / (3960 x efficiency)

Review note

Confirm units before comparing results. If the value controls a design choice, check it against adopted criteria and project-specific inputs.

Use this result

Use horsepower and rounded motor size as a preliminary equipment screen.

Check before use
Confirm flow, head, specific gravity, and efficiency before comparing to motor sizes.
Common pitfall
Assumed efficiency can move the required horsepower enough to change motor selection.
Next step
NPSH Calculator

Input evidence

Confirm these values before using the result.

  • Pump flow (GPM)
  • Total head (ft)
  • Specific gravity
  • Pump efficiency

Authority basis

Check jurisdiction, AHJ, submittal, and edition records before using this result as project evidence.

State and Local Code Adoption WorkflowAHJ Contact ChecklistFire Protection Submittal ChecklistNFPA 13, 72, and 25 Edition Basis Worksheet

Record retention

Save the PDF after project fields, inputs, and results are set.

PDF includes

  • Project header and calculator inputs
  • Computed result rows and warnings
  • Formula, reference basis, and professional boundary

Check before filing

  • Input traceability
  • Method review
  • Output reasonableness
  • Professional boundary

Open next

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Engineering disclaimer
NFPA in USA provides engineering workpapers, calculation checks, and reference tables for project screening and coordination. Final design decisions, code interpretations, submittals, and acceptance records must be completed by qualified professionals and verified against the adopted code, project criteria, listings, and Authority Having Jurisdiction requirements. This site does not issue signed or sealed engineering documents.

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FAQ

What is this Fire Pump Horsepower calculator for?+
Use it to compute a defined fire protection value from documented inputs, then retain the inputs, result, formula, and warnings with the project record.
Are the results suitable for permit submission?+
Use the saved record only after it is checked against adopted code, project criteria, equipment listings, and AHJ requirements.