Tool · independent publisher, not a contractor
Prepare for your AC sizing visit
This tool does not size your AC. It builds a one-page prep sheet with the facts a contractor's Manual J load calculation needs, so every quote is sized from the same information.
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Build your prep sheet
The tool itself sends nothing to us; your entries stay in this tab. Site analytics are described in the privacy policy.
How to use the tool
- Floor area. Enter the conditioned square feet: the rooms the system will cool. Leave out the garage and any room you do not plan to cool. Your property record or an old appraisal usually lists it.
- Rooms and ceilings. Count the rooms with a supply register or that you want cooled. Pick the ceiling height most rooms have, or "vaulted" if any room opens to the roof.
- Location. Coast, basin or valley. This is the single biggest local driver of cooling load in Los Angeles County.
- Insulation, windows, sun. Answer what you know. "Don't know" is a fine answer; it tells the contractor to check.
- Year built and problem rooms. The year hints at original ducts and insulation. Name the rooms that run hot and the time of day.
- Print or save as PDF. The button opens your browser's print dialog. Bring a copy to every estimate visit.
What the tool computes, exactly
Almost nothing, on purpose. The sheet repeats your answers back in a table and does one piece of arithmetic: floor area divided by 600, rounded to the nearest half ton. That number appears in small type as "budgeting context only".
We print it because LA price guides list central AC prices by tonnage and pair each size with a floor area at roughly 600 square feet per ton. With the half-ton figure you can find the right row on the cost page. It is not a load calculation and does not account for any other answer on the sheet.
If floor area is blank or zero, the tons line disappears and the sheet shows "not given". Nothing else on the sheet depends on the tons figure.
Worked examples
The sizing prep sheet prints a budgeting line in tons that depends only on floor area, at 600 square feet per ton. Here is what it shows for three common LA house sizes; the other answers on the form do not change it.
| Floor area entered | Area ÷ 600 | Printed on the sheet |
|---|---|---|
| 1,000 sq ft | 1.67 | about 1.5 tons |
| 1,450 sq ft | 2.42 | about 2.5 tons |
| 1,800 sq ft (the default) | 3.00 | about 3 tons |
| 2,700 sq ft | 4.50 | about 4.5 tons |
Take the 1,450 sq ft case. A 1950s house in Van Nuys with little attic insulation, single-pane windows and a west-facing living room will likely need more than 2.5 tons on a Manual J. A remodeled house of the same size in Santa Monica, with new insulation and double-pane glass, may need less. The sheet gives both contractors the facts that explain the gap.
Why location in Los Angeles changes the answer
A contractor sizes for a hot design day, and the number of hot days varies more across this county than most people expect. NOAA's 1991–2020 normals for five stations:
| Station | Days ≥ 90 °F | Days ≥ 100 °F | Cooling degree days |
|---|---|---|---|
| LAX | 4.8 | 0.2 | 720 |
| Long Beach airport | 23.3 | 1.9 | 1,166 |
| Downtown LA (USC) | 25.6 | 1.8 | 1,296 |
| Burbank airport | 53.9 | 7.2 | 1,481 |
| Woodland Hills | 115.3 | 35.6 | 1,819 |
NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal (stations USW00023174, USW00093134, USW00023152, USC00049785), retrieved 2026-09-29.
The coast also sits in a different building climate zone from the Valley. Los Angeles County spans building climate zones 6, 8, 9, 14 and 16. The coast (Santa Monica, Long Beach) is zone 6 and the San Fernando Valley zone 9, so the same change-out can carry different tests a few miles apart. Look up an address with the CEC climate zone tool. The zone matters for the Title 24 tests on the change-out, covered in our Title 24 guide, and is one of the inputs a Manual J uses. For more on the split, see coastal vs Valley cooling.
At the estimate visit
- Give the same sheet to every contractor.
- Ask each to run a Manual J and give you the result in writing: the heat gain in Btu/h and the equipment size they chose.
- If two quotes differ by a ton or more, ask each to walk through the inputs. One of them usually assumed something the sheet already answers.
- Check the quote names the permit. In the City of Los Angeles it comes from LADBS; see permits in Los Angeles.
HyreHVAC explains what a Manual J load calculation covers. If a contractor sizes from floor area alone, read what an oversized AC does before you sign.
What this tool does not do
The AC sizing prep sheet is a checklist, not a calculator, and it has firm limits:
- It does not calculate a cooling load or recommend a size. Only a room-by-room Manual J does that.
- It does not check duct size. A bigger condenser on the same ducts can be louder and less efficient; ask whether the ducts were checked.
- It does not price the job. Use the system comparison tool or the cost page for published ranges.
- It does not keep your entries. Print before you close the tab.
We are a publisher, not an HVAC contractor, and nobody from this site visits your home. Questions about the tool go to hello@acinstallationlosangeles.com.
Sources
- NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal (stations USW00023174, USW00093134, USW00023152, USC00049785) (retrieved 2026-09-29)
- California Energy Commission building climate zones (CA State Geoportal); zone assignment by address (retrieved 2026-09-29) — verify before relying on it
- Energy Code Ace (CEC-supported), Single-Family Compliance Manual ch. 9, § 150.2(b)1E–F, 2022 code text; confirm against the 2025 code in force since 1 January 2026 (retrieved 2026-09-29) — verify before relying on it
- LADBS, "Mechanical HVAC Permits" and Express Permits bulletin P/GI 2020-003 (LADBS refused our automated read) (retrieved 2026-09-29) — verify before relying on it
Questions
Can this tool tell me what size AC I need?
No. It collects the facts a contractor needs for a Manual J load calculation, and the Manual J sets the size. Floor area alone misses insulation, windows, sun and ceiling height, which can move the answer by a ton or more.
Why does the location in Los Angeles matter for sizing?
Heat differs sharply across the county. NOAA's 1991–2020 normals show about 5 days a year at 90 °F or above at LAX and about 115 in Woodland Hills. A Valley house can need more cooling than a coastal one of the same size.
What does the "about X tons" line mean?
It divides your floor area by 600 and rounds to the nearest half ton. LA price guides pair sizes with floor area this way, so it helps you read a price table. It is not a sizing result and a contractor should not quote from it.
What should I do with the prep sheet?
Print it or save it as a PDF and give the same copy to each contractor at the estimate visit. Ask each one for the Manual J heat gain in Btu/h and the size chosen, in writing.
Is my information saved or sent anywhere?
No. The sheet is built in your browser tab and nothing you type is sent to us. Closing the tab clears it, so print or save the PDF first.
What if two contractors quote different sizes?
Ask each to show the Manual J inputs they used. A difference of a ton or more usually traces to one assumption, such as insulation, window type or the design temperature. The quote that can explain its number is the one to trust.
Next step
Free quote request
Get a quote to check against these numbers
- Tell us about the job. Service, ZIP, property and timing. The form says right away if your ZIP is outside the area.
- We check the license first. Requests go only to contractors whose CSLB C-20 license we have matched on the state register. If none covers your ZIP yet, we email you and say so.
- Compare what comes back. Line the written quote up against the published ranges and the quote checklist.
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