Fundamentals · calculator
PSI to Feet of Head & Head to PSI Calculator
Convert water pressure between PSI and feet of head in either direction.
Method record
What this calculator measures
Pressure head expresses pressure as the height of a water column. It is a direct bridge between pressure gauges and pump or piping calculations.
Feet of water head = PSI × 2.31 Use it correctly
Calculation steps
- Select PSI or feet of head as the source.
- Enter the measured value.
- Use the converted result in a water-system calculation.
Applicability
Use the model within its limits
This factor assumes water. Other liquids require a specific-gravity correction.
What this result represents
- System
- Fundamentals
- Formula
- Feet of water head = PSI × 2.31
- Review
- Verify safety-sensitive work with qualified guidance.
Worked Field Example
Worked Example: Hydrostatic Column Pressure Calculation
Field Scenario: Determining vertical column head in feet corresponding to 45 PSI measured at a residential well pressure tank.
Given Input Parameters
Step-by-Step Mathematical Solution
- 1 PSI of water column equals 2.30665 feet of vertical head (144 sq in/sq ft ÷ 62.4 lb/cu ft).
- Head (ft) = 45.0 × 2.30665 / 1.0 ≈ 103.80 feet.
- Hydrostatic gradient check: 103.80 ft × 0.4335 PSI/ft = 45.0 PSI.
103.8 feet of water head.
Professional Guidance: If pumping heavier liquids such as brine (SG = 1.15), vertical head for the same 45 PSI would be 103.8 / 1.15 = 90.26 feet.
Quick Answer & Key Principles
Why Does 1 PSI Equal 2.307 Feet of Water Head?
Direct Answer: 1 PSI equals 2.307 feet of water head because a one-foot tall column of pure water with a one-square-inch base weighs exactly 0.4335 pounds at 60°F.
Head (feet) = PSI × 2.307 | PSI = Head (feet) ÷ 2.307 = Head × 0.4335 - One cubic foot of pure water weighs 62.37 lbs at 60°F (15.6°C).
- Dividing 62.37 lbs by 144 square inches gives 0.4331–0.4335 PSI per vertical foot of depth.
- Taking the reciprocal (1 ÷ 0.4335) yields 2.307 feet of water height required to generate 1.0 PSI of hydrostatic pressure.
Engineering Standard Reference
Water Pressure to Vertical Feet of Head Conversion Matrix
Direct conversion between gauge pressure (PSI) and vertical column height (feet and meters of head) for water at 60°F:
| Water Pressure (PSI) | Feet of Head (ft H₂O) | Meters of Head (m H₂O) | Bar Equivalent | Typical Hydrostatic Elevation |
|---|---|---|---|---|
| 5 PSI | 11.5 ft | 3.5 m | 0.34 Bar | Single-story residential rooftop tank lift |
| 10 PSI | 23.1 ft | 7.0 m | 0.69 Bar | Two-story residential plumbing vertical rise |
| 20 PSI | 46.1 ft | 14.1 m | 1.38 Bar | NFPA minimum municipal fire residual pressure |
| 40 PSI | 92.3 ft | 28.1 m | 2.76 Bar | Submersible well pump cut-in pressure head |
| 50 PSI | 115.4 ft | 35.2 m | 3.45 Bar | Elevated municipal water tower height (~115 ft) |
| 60 PSI | 138.4 ft | 42.2 m | 4.14 Bar | Submersible well pump cut-out pressure head |
| 100 PSI | 230.7 ft | 70.3 m | 6.89 Bar | High-pressure booster station / multi-stage pump |
Engineering Note: Formula: Head (ft) = (PSI × 2.307) / Specific Gravity. Based on pure water density of 62.37 lbs/cu ft at 60°F.
Engineering FAQs
Frequently Asked Questions
Why does 1 PSI equal 2.31 feet of water?
A 1-foot tall column of water with a 1-square-inch base weighs 0.4335 pounds (since 62.4 lb/ft³ ÷ 144 in²/ft² = 0.4335 lb/in³). Taking the reciprocal: 1 ÷ 0.4335 = 2.30665 feet of water per PSI.
How does fluid temperature affect the PSI-to-feet conversion?
As water heats up, it expands and its density decreases. At 180°F, water density drops to 60.58 lb/ft³, which increases the conversion factor to 1 PSI = 2.377 feet of head.
Why do pump manufacturers rate performance in feet of head rather than PSI?
A centrifugal pump operating at a given impeller diameter and speed creates a specific physical lift height (head in feet) regardless of fluid density. If pumping gasoline (SG = 0.72) vs water (SG = 1.0), the pump produces the exact same head in feet, but significantly less pressure in PSI.