Transformer Dimensions Chart: Complete Size Guide by kVA [2026]

Quick Answer: A 75 kVA three-phase dry-type transformer measures approximately 43″ × 24″ × 20″
(H×W×D). A 500 kVA unit grows to 64″ × 36″ × 32″. Use our complete dimensions charts below covering 5 kVA to 2,500
kVA across dry-type, oil-filled, and padmount transformers—with clearance requirements and space planning formulas.

“Will it fit?” That’s the question I get asked more than any other—and it’s the one that causes the most expensive surprises. Last year, a building contractor in Houston ordered a 300 kVA three-phase transformer for a tenant buildout. He measured the electrical room doorway at 34 inches wide. The transformer? 32 inches deep, but 58 inchestall on a pallet. It wouldn’t clear the 7-foot ceiling in the corridor. The $8,000 crane rental to lift it through the roof opening wasn’t in anyone’s budget.

After 10+ years of shipping transformers from our factory at Transformer4U,
I’ve learned that dimensions matter just as much as electrical ratings. This guide gives you every measurement you
need—before placing your order.

Why Transformer Dimensions Matter

Getting dimensions wrong doesn’t just mean a tight squeeze—it can violate code and endanger lives:

How to Read Transformer Dimensions (H × W × D)

All dimensions in this guide follow the standard H × W × D convention:

• Height (H): Top of enclosure to bottom (including mounting feet, excluding lifting lugs)
• Width (W): Left side to right side (widest point of enclosure)
• Depth (D): Front to back (including conduit box if applicable)

🔧 Factory Insight: Catalog dimensions typically show the enclosure only. Always add 2-4
inches to height for lifting lugs and 3-6 inches to depth for conduit connections. I’ve seen installers plan based
on catalog dimensions only to find the unit physically can’t connect to their bus duct.

Single-Phase Dry-Type Transformer Dimensions

Data based on typical 480V primary / 120/240V secondary NEMA 2 enclosed configurations. Dimensions vary ±10% by
manufacturer and voltage class.

For detailed specifications including wiring diagrams and full load amps:

• 5 kVA Single-Phase Specifications & Dimensions
• 25 kVA Single-Phase Specifications & Dimensions
• 50 kVA Single-Phase Specifications & Dimensions
• 75 kVA Single-Phase Specifications & Dimensions
• 100 kVA Single-Phase Specifications & Dimensions

Three-Phase Dry-Type Transformer Dimensions

For detailed three-phase specifications:

• 75 kVA Three-Phase Transformer
• 150 kVA Three-Phase Transformer
• 300 kVA Three-Phase Transformer
• 500 kVA Three-Phase Transformer
• 1000kVA Three-Phase Transformer
• 2500 kVA Three-Phase Transformer

🔧 Factory Insight: At our facility, three-phase units above 300 kVA are often shipped without
enclosures to reduce shipping dimensions. The core-and-coil assembly is 6-10 inches narrower and shorter than the
enclosed unit. If your access path is tight, ask your manufacturer about field-installing the enclosure after
positioning the transformer.

Oil-Filled Transformer Dimensions

Oil-filled (liquid-immersed) transformers are larger than dry-type due to the steel tank, radiator fins, conservator,
and bushings. Plan for approximately 15-25% larger footprint than dry-type at the same kVA rating.

Dimensions include tank body, exclude radiator fins (add 6-12″ per side for radiators on units ≥300 kVA). Height
excludes bushings (add 8-16″ for HV bushings).

For detailed oil-filled specifications:

• 75 kVA Oil-Filled Transformer
• 500 kVA Oil-Filled Transformer
• 1000 kVA Oil-Filled Transformer
• 2500 kVA Oil-Filled Transformer

⚠️ Critical Note: Oil-filled transformer dimensions in catalogs often omit radiator fins and
bushings. A 1,000 kVA oil-filled unit with radiators and HV bushings can be 24+ inches wider and 16+ inches
taller than the tank dimensions alone. Always request the overall shipping dimensions from
your manufacturer.

Padmount Transformer Dimensions

Padmount transformers have a distinctive rectangular steel enclosure designed for ground-level installation on a
concrete pad. Their dimensions include the tamper-resistant cabinet.

For detailed padmount specifications:

• 75 kVA Padmount Transformer
• 500 kVA Padmount Transformer
• 1000 kVA Padmount Transformer
• Padmount Transformer Sizing Chart

Size Comparison: Dry-Type vs Oil-Filled vs Padmount

How do the three transformer types compare in physical size at the same kVA rating?

Key Insight: Padmount transformers have the largest footprint (W × D) because their squat,
wide design is optimized for ground-level installation. Dry-type transformers are the most compact, making them
ideal for indoor spaces where floor area is limited.

Installation Clearance Requirements

Knowing the transformer dimensions is only half the equation. You also need proper clearances per the National Electrical Code (NEC):

Quick Space Planning Formulas

Use these formulas to calculate total installation space requirements:

Indoor Electrical Room (Dry-Type)

Min. Room Width = Transformer Width + 72" (36" clearance × 2 sides)
Min. Room Depth = Transformer Depth + 72" (36" front + 36" rear)
Min. Room Height = Transformer Height + 18" (12" top + 6" for lifting lugs)
Total Floor Area (sq ft) = (Room Width × Room Depth) ÷ 144

Example: 500 kVA three-phase (64″ H × 36″ W × 32″ D):

• Room Width = 36 + 72 = 108″ (9 feet)
• Room Depth = 32 + 72 = 104″ (8.7 feet)
• Room Height = 64 + 18 = 82″ (6.8 feet minimum ceiling)
• Total Floor Area = 108 × 104 ÷ 144 = 78 sq ft minimum

Outdoor Concrete Pad (Padmount)

Min. Pad Width = Transformer Width + 12" (6" overhang each side)
Min. Pad Depth = Transformer Depth + 12"
Pad Thickness = 4-6" reinforced concrete

🔧 Pro Tip from the Factory: When designing an electrical room for a transformer, I always
recommend adding 25% extra floor area beyond the NEC minimum. This accounts for cable trays, conduit bends, and the
inevitable need to service or even replace the transformer with a larger unit years later. The marginal cost of a
slightly larger room is nothing compared to a future renovation.

What Affects Transformer Dimensions?

Temperature Rise Impact: A 500 kVA transformer designed for 80°C temperature rise is physically
larger than one designed for 150°C rise—because the lower-rise unit needs more conductor material to reduce I²R
losses. If floor space is constrained, consider a 150°C rise design. For a deeper understanding of temperature
ratings, see our Transformer
Nameplate Guide.

Doorway & Access Path Planning Guide

One of the most overlooked aspects of transformer installation is ensuring the unit can physically reach the
electrical room. Here’s a quick reference for common building access points:

⚠️ Safety Warning: I’ve seen crews try to tilt a 750 kVA transformer to fit through a standard
door. The unit weighs 2,500 lbs—tilting it risks dropping it, damaging the core windings, and injuring workers. If
the transformer doesn’t fit through the planned access path, remove a wall panel or use a crane through the roof.
Never try to force it.

Frequently Asked Questions

What are the dimensions of a 75 kVA transformer?

A 75 kVA single-phase dry-type transformer typically measures 46″ × 26″ × 20″ (1168 × 660 × 508 mm).
The same rating in three-phase measures 43″ × 24″ × 20″ (1092 × 610 × 508 mm). Oil-filled versions
are approximately 15-20% taller and wider due to the steel tank. See our 75 kVA
specifications for complete data.

What are the dimensions of a 500 kVA transformer?

A 500 kVA three-phase dry-type transformer typically measures 64″ × 36″ × 32″ (1626 × 914 × 813 mm)
and weighs approximately 1,900 lbs. This size requires careful space planning with minimum 36-inch clearances on all
sides. See our 500 kVA
specifications.

What are the dimensions of a 1000 kVA transformer?

A 1000 kVA three-phase dry-type transformer typically measures 76″ × 44″ × 38″ (1930 × 1118 × 965
mm). At this size, you need approximately 120 square feet of total installation space including required clearances.
See our 1000 kVA
specifications.

How much clearance do transformers need?

NEC Article 450.21 requires a minimum of 36 inches (914 mm)
clearance on all working sides of a dry-type transformer for maintenance access and air circulation. For oil-filled
transformers rated above 112.5 kVA, additional clearances and fire-rated separations may be required per NEC Article
450.26.

Are oil-filled transformers larger than dry-type?

Yes. Oil-filled transformers are typically 15-25% larger in footprint than equivalent dry-type units
due to the steel tank, radiator fins, conservator, and bushings. However, their superior cooling allows higher
continuous ratings from the same core size.

How do I calculate room size for a transformer?

Total room size = (Transformer Width + 72″) × (Transformer Depth + 72″). This accounts for 36″ clearance on each side
per NEC requirements. For example, a 500 kVA transformer (36″ × 32″) needs a minimum room of 108″ × 104″, or
approximately 78 square feet.

Conclusion

Proper dimension planning prevents the most expensive installation mistakes. Key takeaways from this guide:

• Dry-type transformers are the most compact—ideal for indoor electrical rooms with limited space
• Oil-filled transformers are 15-25% larger in footprint—always account for radiators and
  bushings
• Padmount transformers have the widest footprint—designed for ground-level outdoor pads
• Always add NEC clearances (36″ minimum per working side) to transformer dimensions for room
  planning
• Verify the entire access path—every door, corridor, and elevator from loading dock to
  electrical room
• Request shipping dimensions from your manufacturer—catalog dimensions often exclude accessories

Need Exact Dimensions for Your Project?

Our engineering team at Transformer4U can provide exact dimension drawings,
foundation specifications, and space planning assistance for your specific installation.

Related Articles

• Transformer Weight Chart by kVA: Complete
  Reference Table
• Transformer Sizing Chart: Complete kVA Selection Guide
• Transformer Full Load Amps Chart: Complete FLA Reference
• Transformer Oil Capacity Chart: Complete kVA Reference
• Distribution Transformer Sizing Calculator
• KVA to Amps Calculator
• Padmount Transformer Sizing Chart
• Oil-Filled Transformer Sizing Chart
• Transformer Construction: Core Types and Winding Designs
• Transformer
  Nameplate: How to Read Every Detail

References

• NEC/NFPA 70 – National Electrical Code (Articles 450.21, 450.26, 450.27)
• IEEE C57.12.01 –
  General Requirements for Dry-Type Distribution and Power Transformers
• IEEE 693 – Seismic Design of
  Substations
• NEMA ST 20 – Dry-Type Transformers for General Applications

Disclaimer: Dimensions shown are typical values for standard NEMA 2 enclosed configurations at 480V primary /
208-240V secondary. Actual dimensions vary significantly by manufacturer, voltage class, temperature rise,
winding material, and enclosure type. Always verify with manufacturer datasheets before making installation
decisions. Data references: manufacturer specifications and Transformer4U factory records.