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Math & Numbers

Pump NPSH (Net Positive Suction Head) Calculator & Cavitation Check

Compute the available Net Positive Suction Head (NPSH_a) of a pump and compare it against the required NPSH (NPSH_r) from the pump curve. Head-balance form: NPSH_a = (p_surface_abs - p_vapor) / (ρ·g) + H_static - h_friction. Surface and vapor pressures are absolute; H_static is positive for flooded suction, negative for suction lift. Returns margin (NPSH_a - NPSH_r), ratio (NPSH_a/NPSH_r) and a classification: safe, marginal (margin < 0.5 m), or cavitation likely. If NPSH_r = 0, only NPSH_a is reported. Pressure in Pa/kPa/bar/atm/psi, length in m/ft, density in kg/m³/g/cm³/lb/ft³.

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Quick start

Call this tool from your code in three languages.

cURL
curl -X POST 'https://api.elysiatools.com/en/api/tools/pump-npsh-calculator' \
  -H 'Content-Type: application/json' \
  -d '{"surfacePressure":1,"pressureUnit":"atm","vaporPressure":2.34,"vaporPressureUnit":"kPa","staticHead":2,"staticHeadUnit":"m","frictionLoss":0.5,"frictionUnit":"m","density":1000,"densityUnit":"kg/m3","gravity":9.81,"npshRequired":3,"npshUnit":"m","decimalPlaces":4}'

© 2026 Elysia Tools. Developer documentation.

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API reference

Send a POST request with your inputs as JSON. File parameters require a separate upload first.

Endpoint

HTTP
POST https://api.elysiatools.com/en/api/tools/pump-npsh-calculator

Parameters

NameTypeRequiredDescription
surfacePressurenumberYesAbsolute pressure at the liquid surface (p_surface). Enter in the selected Pressure Unit.
pressureUnitselectNo—
vaporPressurenumberYesAbsolute vapor pressure of the liquid at pumping temperature (p_vapor). Enter in the selected Vapor Pressure Unit.
vaporPressureUnitselectNo—
staticHeadnumberYesElevation of liquid surface above pump centerline (H_static). Positive if liquid level is above the pump (flooded suction), negative for suction lift. Enter in the selected Static Head Unit.
staticHeadUnitselectNo—
frictionLossnumberNoSuction-line friction head loss (h_friction), already computed. Enter in the selected Friction Loss Unit.
frictionUnitselectNo—
densitynumberNoLiquid density (ρ). Enter in the selected Density Unit.
densityUnitselectNo—
gravitynumberNoGravitational acceleration g in m/s².
npshRequirednumberNoThe pump's required NPSH (NPSH_r) from its curve. Enter in the selected NPSH Unit. If 0, the cavitation comparison is skipped and only NPSH_a is reported.
npshUnitselectNo—
decimalPlacesnumberNo—

Response format

JSON result

JSON
{
  "key": {...},
  "metadata": {
    "key": "value"
  },
  "error": "Error message (optional)",
  "message": "Notification message (optional)"
}

MCP integration

Add this tool to your Model Context Protocol server so AI agents can list and call it.

Server configuration

Add this block to your MCP client configuration:

mcp.json
{
  "mcpServers": {
    "elysiatools-pump-npsh-calculator": {
      "name": "pump-npsh-calculator",
      "description": "Compute the available Net Positive Suction Head (NPSH_a) of a pump and compare it against the required NPSH (NPSH_r) from the pump curve. Head-balance form: NPSH_a = (p_surface_abs - p_vapor) / (ρ·g) + H_static - h_friction. Surface and vapor pressures are absolute; H_static is positive for flooded suction, negative for suction lift. Returns margin (NPSH_a - NPSH_r), ratio (NPSH_a/NPSH_r) and a classification: safe, marginal (margin < 0.5 m), or cavitation likely. If NPSH_r = 0, only NPSH_a is reported. Pressure in Pa/kPa/bar/atm/psi, length in m/ft, density in kg/m³/g/cm³/lb/ft³.",
      "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=pump-npsh-calculator",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

List available tools

After connecting to the SSE endpoint, list the exposed tools:

tools/list
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Call this tool

Invoke the tool by its id, passing arguments built from its parameters:

tools/call
{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "pump-npsh-calculator",
    "arguments": {
  "surfacePressure": 1,
  "pressureUnit": "atm",
  "vaporPressure": 2.34,
  "vaporPressureUnit": "kPa",
  "staticHead": 2,
  "staticHeadUnit": "m",
  "frictionLoss": 0.5,
  "frictionUnit": "m",
  "density": 1000,
  "densityUnit": "kg/m3",
  "gravity": 9.81,
  "npshRequired": 3,
  "npshUnit": "m",
  "decimalPlaces": 4
}
  }
}
Chain multiple tools in one session with a comma-separated toolId list, e.g. /mcp/sse?toolId=png-to-webp,jpg-to-webp,gif-to-webp (max 20).

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