Case &ContrastFree calculators

Science & entered-assumption arithmetic

Pump Affinity Law Scenario Calculator

For an ideal fixed-geometry centrifugal-pump similarity scenario, r = new speed / reference speed.

209 / PUMP AFFINITY LAW SCENARIO

Your numbers.
A clearer decision.

Free to use. No signup.
Inputs stay in this browser.

Starting values are illustrative. Use your own costs, rates and assumptions.

INPUT GROUP 01

Entered quantities and model assumptions

Illustrative defaults are examples. Replace them with matching measurements, reviewed properties and actual quote terms.

Check the assumptions before acting on a result.

Read the method and example

YOUR CALCULATION

Apply ideal fixed-geometry speed-ratio similarity.

New / reference rotational speed

0.8

Ideal scaled flow · entered flow units

16

Ideal scaled head · m

16

Ideal scaled shaft power · kW

2.56

Keep the calculation

Saving is optional and stays on this device. Unsaved edits are not kept when you leave. CSV includes every input and the current results.

Illustrative inputs loaded. Replace them with your own assumptions.

How the pump affinity law scenario calculator works

For an ideal fixed-geometry centrifugal-pump similarity scenario, r = new speed / reference speed. Flow scales by r, head by r² and shaft power by r³. Reference speed must be positive, and all reference quantities describe one matching pump point and fluid.

This does not find the operating point where a pump curve meets the actual system curve. Static head, changing efficiency and real limits can invalidate simple electrical-savings expectations. No impeller trimming, NPSH, safe rotational range, motor size or pump installation is recommended by the result.

Quantities use the stated units and finite bounded inputs. Whole purchases round up under the documented model; cost components round half-up to cents before totals are summed. Undefined ratios stay unavailable. π and logarithms use normal numeric precision. Display rounding does not alter the entered assumptions.

Worked example

At 800/1,000 = 0.8 speed ratio, 20 m³/h scales ideally to 16, 25 m head to 16 and 5 kW shaft power to 2.56. Setting new speed to 1,000 rpm returns the reference 5 kW.

Sources and assumptions

The source material explains the underlying calculation or pricing structure. Entered prices, costs, schedules and scenario choices are your assumptions; this tool does not obtain supplier quotes or predict actual results.

  • Equipment Electricity Cost

    Estimate electricity use from input power, equipment count and operating time. Apply your energy rate and a separately entered monthly charge.

  • Pump Hydraulic Power

    Hydraulic kW = fluid density × standard gravity 9.80665 m/s² × flow in m³/s × differential head in metres ÷ 1,000.

  • Flow-Weighted Concentration

    Calculate a nonreactive combined concentration from up to three matched stream flows and constituent concentrations. See each stream’s contribution to the total mass rate.

  • Commercial Water & Sewer Cost

    Assemble two water tiers, a separately entered sewer billing quantity, fixed charges and a signed adjustment.

Calculation methods, testing and sources · Practical calculation guides