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Well Pump Rate Calculator

Work out well pump rate instantly with clear inputs, formula shown and shareable results.

About Well Pump Rate Calculator

The Thiem equation gives steady confined-aquifer well yield as Q = 2 pi T s / ln(R/rw). With transmissivity 250 m2/day, 6 m of drawdown, a 0.15 m well and a 300 m radius of influence, the yield is about 1240 m3/day or 14.4 L/s. Because the well radius enters logarithmically, doubling the borehole diameter adds only a few percent.

Formulas

Thiem equation

Q = 2 pi T s / ln(R / rw)

Specific capacity

capacity = Q / drawdown

Worked example

With the default values below, Well Pump Rate Calculator returns Sustainable Pump Rate of 1,239.96. Change any input above and every figure here is recalculated in your browser.

Inputs used

Aquifer transmissivityminimum 0 m2/day
250 m2/day
Available drawdownminimum 0 m
6 m
Well radiusminimum 0 m
0.15 m
Radius of influenceminimum 0 m
300 m

Results

Sustainable Pump Rate
1,239.96 m3/day
Same Rate In Litres Per Second
14.351
Specific Capacity
206.66 m3/day per m
Logarithmic Radius Ratio
7.601

Step by step

  1. 1Values used
  2. 2Thiem equation
  3. 3Specific capacity
  4. 4Sustainable Pump Rate= 1,239.96 m3/day
  5. 5Same Rate In Litres Per Second= 14.351
  6. 6Specific Capacity= 206.66 m3/day per m
  7. 7Logarithmic Radius Ratio= 7.601

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does a bigger borehole help so little?

Because the radius appears inside a logarithm. Yield is set by aquifer transmissivity, not hole size.

What is the radius of influence?

The distance at which drawdown becomes negligible. It grows with pumping time and is often estimated rather than measured.

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Well Pump Rate Calculator – Calculate Sustainable Pump Rate