700 Sq Ft Apartment AC BTU
Worked AC BTU calculation for a 700 square foot living room in zone 4 (Mid-Atlantic, Ohio Valley).
Reviewed May 22, 2026
Recommended
18,000BTU/hr
≈ 1.5 tons cooling capacity
Acceptable range: 15,786–21,048 BTU/hr
Your room or space
Enter the room characteristics, then click Calculate to see the recommended BTU, the equipment options that fit, the math step-by-step, and what the calculator does not account for.
+600 BTU per person above 2
Recommended cooling capacity
18,000
BTU/hr
≈ 1.5 tons · 5.28 kW
That number is the rate at which the AC must remove heat from the space at peak summer conditions. A 18,000 BTU/hr unit moves the same amount of heat per hour as it would take to melt about 125.0 lb of ice per hour — the "ton" unit comes from exactly that physics, with 1 ton = 12,000 BTU/hr = melting 2,000 lb of ice in 24 hours.
Raw calculation
17,540
BTU/hr before rounding to nearest standard equipment size
Acceptable range
15,786–21,048
BTU/hr (within Manual S tolerance, −10% / +20%)
BTU per sq ft
25.1
For your 700 sq ft input (US average is 22 BTU/sq ft at zone 4)
Where your size lands on the equipment scale
The horizontal bar below maps standard residential equipment sizes from window units on the left to whole-house central AC on the right. Your recommended capacity sits in the highlighted region; the shaded band shows the acceptable range Manual S tolerates.
Equipment class for 18,000 BTU/hr
At this capacity the practical equipment options narrow to a specific class. Here is what that class actually looks like and where its trade-offs land.
The size where mini-split starts making sense
Ductless mini-split or large window unit
14,000 – 18,000 BTU/hr
At 18,000 BTU/hr, the size pushes window AC offerings to their high end. A single-zone mini-split delivers the same capacity at SEER2 20+ (vs SEER2 14 for a window unit), runs quieter, and serves the room aesthetically rather than blocking a window. The trade-off is installation: a mini-split needs a licensed HVAC contractor and $3,000–$5,000 of labor and equipment versus $500–$800 for a window unit.
Standard equipment sizes and where yours falls
Residential AC equipment is manufactured in fixed BTU/hr increments, not continuous sizes. Rounding the raw calculation (17,540 BTU/hr) to the nearest standard size gives you the actual equipment you can buy.
| Standard size | BTU/hr | Tons | Equipment class | Status |
|---|---|---|---|---|
| 5,000 BTU/hr | 5,000 | 0.42 | Window air conditioner | — |
| 6,000 BTU/hr | 6,000 | 0.50 | Window air conditioner | — |
| 8,000 BTU/hr | 8,000 | 0.67 | Window air conditioner | — |
| 10,000 BTU/hr | 10,000 | 0.83 | Window unit or portable AC | — |
| 12,000 BTU/hr | 12,000 | 1.00 | Window unit or portable AC | — |
| 14,000 BTU/hr | 14,000 | 1.17 | Ductless mini-split or large window unit | — |
| 18,000 BTU/hr | 18,000 | 1.50 | Ductless mini-split or large window unit | Recommended |
| 24,000 BTU/hr | 24,000 | 2.00 | Central AC or multi-zone mini-split | — |
| 30,000 BTU/hr | 30,000 | 2.50 | Central AC or multi-zone mini-split | — |
| 36,000 BTU/hr | 36,000 | 3.00 | Central AC or multi-zone mini-split | — |
| 48,000 BTU/hr | 48,000 | 4.00 | Central AC or multi-zone mini-split | — |
| 60,000 BTU/hr | 60,000 | 5.00 | Central AC or multi-zone mini-split | — |
How the 18,000 BTU/hr number was computed
The calculator multiplies a baseline (22 BTU per sq ft at zone 4, average insulation, 8-ft ceilings, normal occupancy) by climate, ceiling, sun, insulation, and space-type factors, then adds adjustments for extra occupants and kitchen use. Each step is shown below so you can re-run the math by hand or adjust an input and predict the result.
| Baseline | 700 sqft × 22 | = 15,400 BTU |
| × Climate factor (zone 4) | × 1 | |
| × Ceiling factor (8 ft) | × 1 | |
| × Sun factor (mixed) | × 1 | |
| × Insulation factor (average) | × 1 | |
| × Space-type factor (living-room) | × 1.1 | |
| Multiplicative subtotal | = 16,940 BTU | |
| + Occupancy adjustment (3 occupants, +600 BTU per person above 2) | + 600 BTU | |
| Raw calculation | = 17,540 BTU | |
| Rounded to nearest standard equipment size | = 18,000 BTU/hr |
What this calculator does NOT account for
- Air leakage by measurement. The "insulation level" input lumps insulation and infiltration together. A house tested at 12 ACH50 on a blower door performs differently than a 4 ACH50 house even with the same wall and attic R-values; the calculator cannot distinguish without the test data.
- Specific window orientation. "Sun exposure" is a coarse three-way input. A south-facing wall of single-pane glass produces very different load than the same square footage of triple-pane north-facing glass, and the calculator averages across orientations.
- Duct losses to unconditioned space. A central AC with leaky attic ducts loses 20–30% of supply air before it reaches the room. The calculator output is the load at the room boundary; for whole-house central AC sizing the duct system condition matters separately.
- Latent vs sensible split. The output is total cooling capacity. In humid climates the AC also has to remove water vapor (latent load), which is sized via sensible heat ratio at equipment-selection time. For whole-house humid-climate sizing, the AC size calculator framing handles this; the BTU calculator does not separate sensible and latent.
- Internal heat gain from specific appliances. Multiple gaming computers running 24/7, server racks, professional cooking ranges, or grow lights add load above the calculator's defaults. For unusual loads, add 1,500–3,500 BTU/hr per kilowatt of continuous electrical input.
For permit-grade sizing — for example, when a contractor must size equipment for a new install or a rebate program requires Manual J documentation — use the Manual J load calculator or hire a credentialed practitioner using ACCA-approved software.
What this calculation is
A 700 square foot apartment is a typical one-bedroom in many US cities. A mini split sized in the 14,000 to 18,000 BTU range usually handles the cooling load comfortably. The calculation assumes a typical apartment envelope: climate zone 4, average insulation, mixed sun, and a 2 to 3 occupant household.
How this calculation was reached
The calculator starts with a baseline of 22 BTU per square foot and applies multiplicative adjustment factors for climate, ceiling height, sun exposure, insulation, and space type. It then adds fixed amounts for additional occupants and kitchen heat gain. For this scenario:
- Baseline: 700 sqft × 22 BTU/sqft = 15,400 BTU
- × Climate factor (zone 4 (Mid-Atlantic, Ohio Valley)): 1
- × Ceiling factor (8 ft): 1
- × Sun factor (mixed (typical)): 1
- × Insulation factor (average (meets current code)): 1
- × Space-type factor (living room): 1.1
- = Subtotal: 16,940 BTU
- + Occupancy (3 occupants, 1 above baseline): 600 BTU
- = Final raw: 17,540 BTU
- Rounded to nearest standard equipment size: 18,000 BTU
Adjust the inputs
The calculator above is interactive. Change any input — square footage, climate zone, ceiling, insulation, sun exposure, space type, occupants, or kitchen flag — and the result updates live. Use “Reset to defaults” to return to the values shown on this page.
Methodology
This calculation follows the ENERGY STAR room AC sizing guide and Manual J 8th Edition residential load calculation, simplified for whole-room sizing. The methodology is documented in the AC BTU chart article and verified against ACCA reference cases per our verification methodology. Limitations: whole-room estimate only, does not perform room-by-room load calculation, and does not include duct losses to unconditioned spaces.
Try other examples
Compare to nearby scenarios with different square footage or space type.
- 500 Sq Ft Room AC BTU
12,000 BTU (≈ 1 tons)
- 400 Sq Ft Room AC BTU
10,000 BTU (≈ 0.75 tons)
- 1,000 Sq Ft House AC BTU
24,000 BTU (≈ 2 tons)
- 1,200 Sq Ft House AC BTU
30,000 BTU (≈ 2.5 tons)
- 1,500 Sq Ft House AC BTU
36,000 BTU (≈ 3 tons)
Reviewed May 22, 2026