Hydronic Radiant Floor PEX Tubing Linear Footage, Loop Count & GPM Flow Calculator

Compute radiant floor PEX linear feet, manifold loop count (≤300 ft/loop), and GPM at ΔT=15°F.

Total Radiant PEX Tubing Required
1,680 linear ft
Manifold Loops Required (≤ Max Length) 6 loops
Average Tubing Length per Loop 280 ft/loop
Design Hydronic Flow (@ ΔT = 15°F) 4 GPM
Inputs
⚡ Scenarios:
sq ft
Net heated floor area in square feet.
inches OC
PEX tube on-center spacing (6", 8", 9", or 12" OC).
ft/loop
Maximum allowable single loop length (≤300 ft for 1/2" PEX).
BTU/h·ft²
Design radiant floor output (BTU/hr per sq ft).
Results & Graph
Total Radiant PEX Tubing Required
1,680 linear ft
Manifold Loops Required (≤ Max Length)
6 loops
Average Tubing Length per Loop
280 ft/loop
Design Hydronic Flow (@ ΔT = 15°F)
4 GPM

Total Radiant PEX Tubing Required

Graph 1 • Radiant Floor PEX Loops • Domain Architecture & Live Telemetry Maps Heated Floor Area Sq Ft, Pex On Center Spacing Inches, Max Single Loop Length Feet through Radiant Floor PEX Loops Formula.
INPUT PARAMETERS • Heated Floor Area : 1200 sq ft • Pex On Center Spac: 9 inches OC • Max Single Loop Le: 280 ft/loop ∑ F(x) Radiant Floor PEX Loops DESIGN OUTPUT 1,680 linear ft Manifold Loops Required : 6 loops Average Tubing Length pe: 280 ft/loop
Graph 2 • Total Radiant PEX Tubing Required Across Heated Floor Area Sq Ft Sweep (40% → 160%) Evaluates TotalPEX_ft = (HeatedArea_ft² × (12 / Spacing_in)) × 1.05; Loops = cei across 7 operating points (current input highlighted).
0 linear 1.5k linear 3.0k linear 672 480sq ft 1.0k 720sq ft 1.3k 960sq ft 1.7k 1.2ksq ft 2.0k 1.4ksq ft 2.4k 1.7ksq ft 2.7k 1.9ksq ft
Graph 3 • Joint Sensitivity: Heated Floor Area Sq Ft × Pex On Center Spacing Inches Compares Total Radiant PEX Tubing Required when Pex On Center Spacing Inches is shifted +25% (solid) vs. −25% (dashed).
0 linear 1.6k linear 3.2k linear --- Pex On Center Spacing Inches @ 75% 941 -30% 1.1k -15% 1.3k +0% 1.5k +15% 1.7k +30%
Summary: Heating 1,200 sq ft at 9" OC requires 1,680 linear ft of PEX split across 6 manifold loops (~280 ft/loop) with 4 GPM flow.
Summary: Heating 1,200 sq ft at 9" OC requires 1,680 linear ft of PEX split across 6 manifold loops (~280 ft/loop) with 4 GPM flow.
⚡ Send result to: Concrete & Sq Ft →Ohm's Law & Voltage Drop →Roofing, Stairs & BTU →
Interactive chart & math engine powered by CalculatorGraph

Formula & Mathematical Methodology: Radiant Floor PEX Loops Formula

TotalPEXft = (HeatedAreaft² × (12 / Spacingin)) × 1.05
Loops = ceil(TotalPEXft / MaxLoopLengthft)
TotalPEX_ft = (HeatedArea_ft² × (12 / Spacing_in)) × 1.05; Loops = ceil(TotalPEX_ft / MaxLoopLength_ft)
  • heatedFloorAreaSqFt: Heated Floor Area Sq Ft (sq ft)
  • pexOnCenterSpacingInches: Pex On Center Spacing Inches (inches OC)
  • maxSingleLoopLengthFeet: Max Single Loop Length Feet (ft/loop)
  • heatLoadBtuPerSqFt: Heat Load Btu Per Sq Ft (BTU/h·ft²)

Rounding: Engineering outputs round to 2–3 decimal places; discrete material bag/unit counts round up via ceiling.

Worked Example: Engineering Scenario: Radiant Floor PEX Loops

Compute radiant floor PEX linear feet, manifold loop count (≤300 ft/loop), and GPM at ΔT=15°F.

  1. Enter your system dimensions, electrical/RF ratings, or environmental conditions.
  2. Evaluate the governing equation: TotalPEX_ft = (HeatedArea_ft² × (12 / Spacing_in)) × 1.05; Loops = ceil(TotalPEX_ft / MaxLoopLength_ft).
  3. Inspect the primary design output, supporting allowances, and 3 SVG schematics.
Result: Computes Radiant Floor PEX Loops via TotalPEX_ft = (HeatedArea_ft² × (12 / Spacing_in)) × 1.05; Loops = ceil(TotalPEX_ft / MaxLoopLength_ft).

Frequently Asked Questions

How does the Hydronic Radiant Floor PEX Tubing Linear Footage, Loop Count & GPM Flow Calculator calculate results?

It evaluates TotalPEX_ft = (HeatedArea_ft² × (12 / Spacing_in)) × 1.05; Loops = ceil(TotalPEX_ft / MaxLoopLength_ft) directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a required dimension or rating?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Does this engineering calculator work offline?

Yes. All calculations run 100% locally in your browser and work offline via the CalculatorGraph PWA.

Construction & Home · Plumbing, Hydronics & Drainage

Hydronic Radiant Floor PEX Tubing Linear Footage, Loop Count & GPM Flow Calculator: inputs, method, and how to read the result

Compute radiant floor PEX linear feet, manifold loop count (≤300 ft/loop), and GPM at ΔT=15°F.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Heated Floor Area Sq Ft: Net heated floor area in square feet.
  • Pex On Center Spacing Inches: PEX tube on-center spacing (6", 8", 9", or 12" OC).
  • Max Single Loop Length Feet: Maximum allowable single loop length (≤300 ft for 1/2" PEX).
  • Heat Load Btu Per Sq Ft: Design radiant floor output (BTU/hr per sq ft).

What the calculation includes

With the default values shown, Total Radiant PEX Tubing Required is 1,680 linear ft. The calculation follows Radiant Floor PEX Loops Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Heated Floor Area Sq Ft from 1,200 sq ft to 1,320 sq ft changes Total Radiant PEX Tubing Required from 1,680 linear ft to 1,848 linear ft. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard NREL, IEEE, ASHRAE, and IRC design equations.
  • Verify final structural, electrical, and mechanical specifications against local building codes.

Scope: Global Engineering & Building Code Standard Check the assumptions and limitations against your situation before relying on the estimate.

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