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Calculators that actually compute
Six client-side tools for commercial rooftop work. Everything runs in your browser — no sign-up, nothing leaves your phone. These are fast planning numbers, not a substitute for a stamped load calc. Read the note under each one.
RTU Cross-Reference & Submittal Finder ↗
The big one for field work. Decode an old unit by model number or filter by specs, get compatible replacement candidates across nine manufacturers, see the swap deltas (config, electrical, heat, curb), and jump straight to each manufacturer’s submittal — right on the iPad. Opens its own full-screen tool.
Rooftop Replacement Survey Checklist ↗
The bulletproof field walk-through so you never leave the roof missing a number. Nine sections — nameplate, electrical, gas, curb & curb-adapter, ductwork, controls, rigging/crane, site logistics, code — with the gotcha behind each line. Includes the curb-adapter fork that forces you to capture the original curb’s hidden duct openings. Tap to check, type measurements in, then print or save a clean PDF. Opens its own full-screen tool.
RTU Tonnage / Quick Load Estimator
Ballpark the cooling tonnage for a commercial space by building type, square footage and climate. Use it to pick a starting unit size before you cut sheets.
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Rule-of-thumb only (sq ft / ton by occupancy, adjusted for climate). High-glass, high-occupancy, or kitchen loads can swing this hard. Confirm with a full Manual N / block load before ordering.
Curb Adapter Decision Tool
Compare your existing roof curb footprint to the new unit's base. Find out whether you're likely looking at a direct fit or a fabricated curb adapter — before you're on the roof with a crane on the clock.
Existing curb / old unit base (outside dimensions, inches)
New unit base (outside dimensions, inches)
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Dimensional comparison only. Always order an adapter built to the exact old + new model numbers from a curb fabricator, and have the roof structure reviewed for any weight increase.
Replace vs. Repair Calculator
Put real numbers on the "do we fix it again or replace it" question. Factors in age, the repair in front of you, energy cost, and simple payback.
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Uses ~$2,200/ton installed and ~18% energy savings as planning assumptions — your market and utility rates vary. Get firm quotes before deciding.
Gas vs. Electric Heat Sizing
Quick heating-load check for a packaged rooftop unit. Get the heating BTU/hr plus a starting gas heat (MBH input) and electric (kW) size, and a fuel recommendation.
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Envelope-based rule of thumb. Tight, well-insulated buildings need less; leaky older shells need more. Confirm with a heat-loss calc and check available gas pressure / electrical capacity.
Tools worth owning for RTU work
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Digital manifold gauge set
Wireless probes beat a hose-and-dial set for commissioning a new packaged unit fast. Worth every penny on a busy swap.
View on Amazon →Rooftop unit lifting rigging
Proper spreader bars and certified slings for setting a package unit. Don't cheap out on what's holding a half-ton over your head.
See the kit →Laser distance measure
Measuring curb openings and clearances solo? A good laser saves trips up the ladder and bad numbers in your estimate.
Check price →