TryBuildCalcPVC Conduit Fill Calculator (PVC Schedule 40 Sizing)
Calculate your PVC conduit size.
🕒 Last updated: August 29, 2026
Inputs
Conductors
Add every conductor being pulled through this conduit — mix as many different wire sizes as needed.
Conductor 1
Conductor 2
Conductor 3
ℹ️EMT, PVC Schedule 40, and RMC have slightly different internal areas at the same trade size — the result compares all three.
Recommended Conduit Size: 1/2" PVC Schedule 40
5 conductors, 37.0% fill (max allowed 40%)
Conductor Breakdown
| Conductor | AWG | Qty | Area |
|---|---|---|---|
| Hot | 10 AWG | × 3 | 0.0633 in² |
| Neutral | 10 AWG | × 1 | 0.0211 in² |
| Ground | 10 AWG | × 1 | 0.0211 in² |
| Total | 5 conductors | 0.1055 in² |
Fill Calculation
Total conductor area: 0.1055 in²
Allowed fill (NEC Table 1, 5 conductors): 40%
1/2" PVC Schedule 40 internal area: 0.285 in² (0.1140 in² allowed at 40%)
Actual fill achieved: 37.0%
Trade Size by Conduit Type
| Conduit Type | Required Trade Size |
|---|---|
| EMT (Electrical Metallic Tubing) | 1/2" |
| PVC Schedule 40 | 1/2" |
| RMC (Rigid Metal Conduit) | 1/2" |
Assumptions Used
Conductor areas per NEC Chapter 9 Table 5 (THHN/THWN-2 insulation). Fill limits per NEC Chapter 9 Table 1 (53% for 1 conductor, 31% for 2, 40% for 3 or more). This is a reference estimate — confirm with a licensed electrician before installation.
Need to check whether each conductor is correctly sized for its load first? Wire Size Calculator →
Sizing the breaker for this circuit next? Circuit Breaker Size Calculator →
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Conduit Fill Calculator.
PVC conduit sizing
PVC Schedule 40 is commonly used for underground runs and corrosive or wet environments — this page is pre-set to PVC with a common 4-conductor branch circuit.
Edit the conductor list above to match your actual circuit.
- PVC Schedule 40 has a slightly smaller internal area than EMT or RMC at the same trade size, since its walls are thicker.
- PVC is a common choice for underground and direct-burial installations, subject to local code depth and protection requirements.
- PVC Schedule 80 (a thicker-walled variant with even less internal area) is not covered by this calculator.
Conduit Fill Formula: How Is It Calculated?
Three NEC Chapter 9 tables work together: conductor areas, allowable fill percentage, and conduit internal areas.
Step 1 — Total Conductor Area
Total Area (in²) = Sum of every conductor's (AWG area × quantity)
Each conductor's cross-sectional area comes from NEC Chapter 9 Table 5 (THHN/THWN-2 insulation).
Step 2 — Allowable Fill Percentage
1 conductor: 53% max fill
2 conductors: 31% max fill
3+ conductors: 40% max fill
Per NEC Chapter 9 Table 1 — based purely on total conductor count, regardless of size.
Step 3 — Required Trade Size
Find smallest trade size where: Conduit Area × Fill % ≥ Total Conductor Area
Checked against NEC Chapter 9 Table 4's internal area for your chosen conduit type (EMT, PVC Schedule 40, or RMC).
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value | Why it is used |
|---|---|---|
| Conductors | 3 distinct sizes, 5 total | Sets total area and fill percentage tier |
| Conduit Type | PVC Schedule 40 | Sets internal area per trade size |
Step 1 — Conductor Area per Row
| Conductor | Calculation | Area |
|---|---|---|
| Hot | 10 AWG area × 3 | 0.0633 in² |
| Neutral | 10 AWG area × 1 | 0.0211 in² |
| Ground | 10 AWG area × 1 | 0.0211 in² |
| Total | 0.1055 in² |
Step 2 — Allowed Fill Percentage
Set once by your total conductor count, per NEC Chapter 9 Table 1.
| Allowed fill (5 conductors, 3+ tier) | 40% |
Step 3 — Checking Each Trade Size in Order
Starting from the smallest PVC Schedule 40 size, each one is checked until the first that has enough allowed area is found.
| Trade Size | Calculation | Allowed Area | Fits 0.1055 in²? |
|---|---|---|---|
| 1/2" | 0.285 × 40% | 0.1140 in² | Yes — this is the answer |
Therefore, for 5 conductors (0.1055 in² total) in PVC Schedule 40, you need 1/2" (0.285 in² total, 0.1140 in² allowed at 40%), running at 37.0% actual fill.
Related Calculators
Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.