# Well Pump Size Calculator

Well pump size calculator for submersible pumps. Estimates required horsepower, GPM demand, and total dynamic head by home size, well depth, and pipe run.

## What this calculates

Sizing a submersible well pump means matching two things: GPM demand at peak use and total dynamic head (TDH). This well pump size calculator covers both. It answers what size well pump do i need for my house by totaling pumping water level, elevation rise, friction loss, and target pressure, then maps the result to the closest standard horsepower on the Goulds and Grundfos sizing charts.

## Inputs

- **Home Size** — options: 1 bedroom / 1 bath (small), 2 bedrooms / 2 baths, 3 bedrooms / 2-3 baths (typical), 4 bedrooms / 3 baths, 5+ bedrooms / 4+ baths (large), Irrigation + home combined — This answers what size well pump do i need for my house
- **Well Depth (total)** (ft) — min 20 — Total drilled depth of the well
- **Pumping Water Level** (ft) — min 10 — Depth to water during pumping (static level + drawdown). Check well log.
- **Elevation Rise to Tank** (ft) — min 0 — Vertical distance from ground level up to the pressure tank
- **Horizontal Pipe Run** (ft) — min 0 — Total horizontal run from well to pressure tank
- **Drop Pipe Size** — options: 3/4 inch (small home, shallow only), 1 inch (standard residential), 1-1/4 inch (deep well / high flow) — Larger pipe reduces friction loss
- **Target Pressure** — options: 30/50 psi switch (40 psi average), 40/60 psi switch (50 psi average, typical), 50/70 psi switch (60 psi, large home)

## Outputs

- **Peak GPM Demand** (gpm) — Gallons-per-minute demand at peak use
- **Total Dynamic Head** (ft) — Sum of lift + elevation + friction + pressure
- **Recommended Pump Size** (HP) — Submersible pump HP rating to meet GPM and TDH
- **Pump Recommendation** — formatted as text
- **Friction Loss** (ft)

## Details

## What Size Well Pump Do I Need for My House?

The answer depends on three things: how many fixtures run at once (GPM), how deep the water is (pumping level), and what pressure you want at the fixtures.

- **1-2 bath home:** 6-7 GPM, typically 1/2 HP if well is under 100 ft
- **3 bath home (typical):** 8 GPM, 3/4 to 1 HP for wells 100-250 ft
- **4+ bath home with irrigation:** 10-15 GPM, 1.5-2 HP for deep wells

## Submersible Well Pump Sizing Chart

| Home Size | Peak GPM | Well Depth | TDH | Recommended HP |
|-----------|----------|------------|-----|----------------|
| 1-2 bath | 6 GPM | 100 ft | 250 ft | 1/2 HP |
| 3 bath | 8 GPM | 200 ft | 350 ft | 1 HP |
| 3 bath + irrigation | 10 GPM | 200 ft | 400 ft | 1.5 HP |
| 4-5 bath | 12 GPM | 250 ft | 450 ft | 2 HP |
| 5+ bath deep | 15 GPM | 400 ft | 600 ft | 3 HP |

This submersible well pump sizing chart is a starting point. Use the calculator above with your actual numbers from the well log.

## Goulds Well Pump Sizing Chart

The Goulds well pump sizing chart (GS series) is the industry reference. Goulds GS models are rated at specific GPM-vs-TDH points on their pump curves. The formula used by the Goulds well pump sizing chart:

**HP = GPM x TDH / (3960 x efficiency)**

Efficiency for submersibles is about 60%. This calculator applies the same formula and rounds up to the nearest standard HP size (1/2, 3/4, 1, 1.5, 2, 3, 5 HP).

## Calculating Total Dynamic Head

- **Pumping water level (lift):** depth to water during pumping, from the well log
- **Elevation rise:** vertical distance from the wellhead up to the pressure tank
- **Friction loss:** about 3.5 ft per 100 ft of 1-inch PVC at 10 GPM
- **Pressure head:** 50 psi = 115 ft (2.31 ft per psi). 40/60 psi switch = 50 psi average.

Add these four numbers for your TDH.

## Well Pump Size Calculator PDF

Pump manufacturers publish a well pump size calculator pdf with worksheet forms: Goulds, Grundfos, Franklin Electric, and Sta-Rite each have one. They all use the same underlying math as this calculator. The advantage of using this tool over a pump size calculator pdf is that it updates in real time as you change inputs.

## Avoid Oversizing

A bigger pump is not better. Oversizing causes:

- Short-cycling that burns out the motor and pressure switch
- Higher electric bills (larger motor, same output)
- Pressure spikes that stress fittings
- Reduced well recovery time

Size to peak demand + 20% safety margin, not 3x.

## Common Well Pump Brands and Sizes

- **Goulds GS series:** 1/2 to 5 HP, 5-25 GPM range
- **Grundfos SQ series:** 1/2 to 3 HP, 5-30 GPM
- **Franklin Electric:** motors for most pump brands, 1/3 to 7.5 HP
- **Sta-Rite / Pentair:** 1/2 to 5 HP residential

## Frequently Asked Questions

**Q: What size well pump do i need for my house?**

A: For a typical 3-bedroom, 2-bath home with a 200 ft well, you need an 8 GPM submersible pump rated for about 350 ft of total dynamic head, which is a standard 1 HP pump. A 1-2 bedroom home usually needs only 1/2 HP; a 4-5 bedroom home with irrigation typically needs 1.5-2 HP.

**Q: How is the submersible well pump sizing chart organized?**

A: A submersible well pump sizing chart lists GPM capacity at multiple TDH values for each HP tier. For example, a 1 HP Goulds 10GS10 delivers 10 GPM at 300 ft or 7 GPM at 400 ft. Pick the row that matches your GPM and TDH, then use the listed HP.

**Q: How do I use the Goulds well pump sizing chart?**

A: The Goulds well pump sizing chart uses the formula HP = GPM x TDH / (3960 x 0.6). Enter your GPM (peak demand) and TDH (pumping level + elevation + friction + pressure head). Round the result up to the nearest standard HP tier: 1/2, 3/4, 1, 1.5, 2, 3, or 5 HP.

**Q: Is there a well pump size calculator pdf I can download?**

A: Goulds, Grundfos, Franklin Electric, and Sta-Rite each publish a well pump size calculator pdf with fill-in worksheet forms. They all use the same math as this tool. The PDFs are fine offline but this online calculator updates instantly as you try different scenarios.

**Q: How do I measure pumping water level if I don't have a well log?**

A: Ask your driller for the original well log, which lists static level and yield. If unavailable, a well contractor can drop a tape or transducer to measure pumping level directly. As a rough estimate, pumping level for a moderate-yield well is 50-100 ft below the static level.

**Q: Can I upgrade to a bigger well pump without any other changes?**

A: Usually no. A larger pump may exceed the well casing's safe yield, causing the pump to run dry and burn out. It may also exceed the pressure tank capacity, causing rapid cycling. Before upgrading, verify well yield (done by a driller in gallons per minute sustained for 4 hours) and match the pressure tank drawdown to the new pump GPM.

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Source: https://vastcalc.com/calculators/construction/well-pump
Category: Construction
Last updated: 2026-04-08