SettingsSettings for this calculationUS
The equipment unit's overall width.
Use the manufacturer's overall unit dimension, not just the base or footprint dimension of the cabinet.
The equipment unit's overall length.
Use the manufacturer's overall unit dimension, not just the base or footprint dimension of the cabinet, and include any base rails, piping stubs, or projections along this side.
The manufacturer's minimum clearance to be maintained around the equipment.
This calculator applies a single clearance value evenly on all four sides; check the manufacturer's data for any side-specific clearance requirements (service-access sides often need more).
Required pad/curb footprint
20 sq ft
Use the specific equipment manufacturer's minimum service clearance requirements (often different on the service-access side vs. other sides) rather than a uniform assumed clearance — this calculator applies the single clearance value you supply evenly on all sides as a simplified estimate.
They open the calculator with your figures already in it
HVAC Equipment Pad/Curb Footprint Calculator: 20 sq ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Pad/curb footprint = (Equipment Width + 2 × Clearance) × (Equipment Length + 2 × Clearance), applying the manufacturer's required service clearance evenly around the equipment's footprint — a standard equipment placement sizing method.
Inputs used
- Equipment Width
- 3 ft
- Equipment Length
- 4 ft
- Required Service Clearance (Each Side, per Manufacturer)
- 6 in
Confidence note: Use the specific equipment manufacturer's minimum service clearance requirements (often different on the service-access side vs. other sides) rather than a uniform assumed clearance — this calculator applies the single clearance value you supply evenly on all sides as a simplified estimate.
What this calculation does not cover
- This is a plan area, not a pad. Thickness, reinforcement and what goes under it come from the unit's operating weight — the wet weight, with the unit charged and any water side full — spread over that footprint against the bearing capacity of the fill beneath. A pad poured thin on soft or uncompacted ground settles unevenly, and what shows it first is the refrigerant piping and duct connections working at the joints.
- A roof curb is dimensioned by the unit, not by clearance. Its plan size matches the equipment's supply and return duct openings and its base rails, so it comes off the manufacturer's curb drawing rather than any formula — and the roof structure under it usually needs framing added between joists to pick up point loads the deck was never designed for. Adding a service clearance to a curb dimension is the wrong shape of answer entirely.
- Service clearance does not have to be concrete, and the clearances that matter most are not service clearances. A technician can stand on gravel, so applying the allowance to all four sides can over-pour a pad by a wide margin. Meanwhile the non-negotiable ones sit outside this arithmetic: discharge clearance above and at the coil face of a condenser or heat pump, separation from a property line, an operable window, a gas meter or a dryer vent, and clear working space at the disconnect.
Part of a bigger job
This trade is one line of a job takeoff. Run the whole job and every other trade comes back with it, off the same measurements.
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Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Pad/curb footprint = (Equipment Width + 2 × Clearance) × (Equipment Length + 2 × Clearance), applying the manufacturer's required service clearance evenly around the equipment's footprint — a standard equipment placement sizing method.
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