BTU to Tons Converter: understand cooling power in seconds
Choosing an air conditioner or chiller gets easier when you speak the right language. Your spec sheet lists cooling in BTU per hour while your contractor talks about “two tons”. This guide explains both and gives you a fast BTU to tons converter you can trust. You will see the exact formula, common values, and real-world sizing tips so your system cools well without wasting energy.
What are BTU and tons of refrigeration
A BTU, or British thermal unit, is the heat needed to raise one pound of water by one degree Fahrenheit. Cooling capacity uses BTU per hour because equipment removes heat over time. Standards groups use the International Table BTU which cleanly relates to watts. One watt equals 3.412142 BTU/h and one BTU/h equals 0.29307107 watts. See definitions and constants from the U.S. NIST.
A ton of refrigeration (TR) is a legacy unit from the ice-making era. One ton measures the cooling required to freeze a short ton of water into ice over 24 hours. Modern standards fix it at 12,000 BTU/h. That round number keeps calculations simple in HVAC work. ASHRAE and DOE publications use the same constant.
BTU ↔ tons conversion formula
The math is straightforward. Use these equations any time:
- Tons =
BTU/h ÷ 12,000 - BTU/h =
Tons × 12,000 - Watts =
BTU/h × 0.29307107 - kW =
Tons × 3.516852842
Those constants come from the accepted relation between the IT BTU and the watt and from the definition of a refrigeration ton. You can verify the BTU–watt factor at the U.S. DOE.
Quick conversion table (BTU/h ⇄ tons ⇄ kW)
Use this small table when you need a fast estimate on site. It covers the most common room AC and split-system sizes.
| BTU per hour | Tons (TR) | Kilowatts (kW) |
|---|---|---|
| 6,000 | 0.5 | 1.76 |
| 9,000 | 0.75 | 2.64 |
| 12,000 | 1.0 | 3.52 |
| 18,000 | 1.5 | 5.28 |
| 24,000 | 2.0 | 7.03 |
| 30,000 | 2.5 | 8.79 |
| 36,000 | 3.0 | 10.55 |
| 48,000 | 4.0 | 14.07 |
| 60,000 | 5.0 | 17.58 |
Step-by-step examples you can copy
Example 1 — Convert 30,000 BTU/h to tons
- Write the formula:
Tons = BTU/h ÷ 12,000. - Substitute:
Tons = 30,000 ÷ 12,000 = 2.5. - Result: a 30,000 BTU/h unit is a 2.5-ton system.
Example 2 — Convert tons to BTU/h
- You have a 1.5-ton split.
- Use
BTU/h = Tons × 12,000. BTU/h = 1.5 × 12,000 = 18,000 BTU/h.
Example 3 — Compare a specification in kW
- Spec sheet lists cooling capacity 7.0 kW.
- Convert to BTU/h:
BTU/h = 7,000 W × 3.412142 = 23,885. - Now tons:
23,885 ÷ 12,000 ≈ 1.99 tons. That system is roughly two tons.
Why 1 ton equals exactly 12,000 BTU/h
The ton of refrigeration traces back to commercial ice plants. Freezing a short ton of water from 32°F water to 32°F ice over one day requires approximately 288,000 BTU of heat removal. Divide by 24 hours and you get 12,000 BTU/h. Modern standards keep this definition to align industry language with historical practice. For background see the entry on ton of refrigeration in the ASHRAE terminology database.
HVAC sizing tips that avoid common mistakes
You want a room that feels comfortable without a power bill that shocks you at the end of the month. Proper sizing matters.
- Start with load. Square footage gives a starting point. Climate zone, insulation level, window orientation, and occupancy all change the answer. The DOE guide to room AC sizing outlines a simple approach for homes.
- Remember sensible vs latent load. Dry climates stress sensible cooling. Humid climates stress moisture removal. The same BTU/h number can behave differently when indoor humidity runs high.
- Don’t oversize. Oversized systems short cycle. Rooms cool quickly then warm again. Comfort drops and humidity control suffers.
- Check supply voltage and breaker capacity. A correct tonnage still fails if the circuit cannot support the running and starting current.
- Look at SEER/EER ratings. Capacity tells you how much cooling you get. SEER tells you how much electricity it takes to deliver that cooling across a season.
BTU vs BTU/h vs kW
Many spec sheets print “BTU” when they actually mean BTU per hour. Capacity is a rate. If you read just “BTU” on a marketing line, assume BTU/h and check the fine print. Engineering texts always use BTU/h for power and BTU for energy. In SI units power uses watts and energy uses joules or kilowatt-hours.
Energy (BTU) ── per hour ──► Power (BTU/h) ──×0.29307107──► Power (W)
▲
│ ÷0.29307107
└────────────── from watts to BTU/h
Most requested BTU to tons conversions
Bookmark this list for quick field checks. Every value uses the exact 12,000 BTU/h per ton constant.
| BTU/h | Tons | kW | Use case |
|---|---|---|---|
| 5,000 | 0.417 | 1.47 | Small bedroom or office |
| 8,000 | 0.667 | 2.35 | Studio or dens |
| 10,000 | 0.833 | 2.93 | Larger bedroom |
| 15,000 | 1.25 | 4.40 | Open living + kitchen |
| 20,000 | 1.667 | 5.86 | Small shop |
| 36,000 | 3.0 | 10.55 | Light commercial zone |
| 72,000 | 6.0 | 21.10 | Rooftop package |
| 120,000 | 10.0 | 35.17 | Small chiller |
BTU to tons converter — FAQ
Is a “ton” here the same as a short ton of weight
No. A ton of refrigeration measures cooling power not mass. It equals 12,000 BTU/h. A short ton in the U.S. equals 2,000 lb of weight. The words sound the same yet they measure different things.
What about metric units
You can express the same cooling capacity in SI units as kilowatts. Multiply tons by 3.516852842 to get kW. Multiply kW by 0.2843451361 to get tons. If you see kW on a European spec sheet this conversion gets you back to familiar tonnage.
Is 12,000 BTU/h always correct
Yes for tonnage. Actual equipment capacity can drift slightly under different test conditions or at different ambient temperatures. The definition of a refrigeration ton stays fixed at exactly 12,000 BTU/h to keep engineering calculations clear.
How do I use tons to size an air conditioner
Use room area as a quick check then adjust for windows, people, and climate. A rough rule places small bedrooms between 0.5 and 0.75 ton. Open living areas can need 1.5 to 2.5 tons depending on solar gain and infiltration. For solid results follow a Manual J load method or use a professional energy model. The DOE explains the basics in its Room Air Conditioners guide.
How do BTU/h, EER, and SEER relate
EER and SEER describe efficiency. Divide BTU/h by input watts to get EER at a test point. SEER averages seasonal performance. High SEER means less electricity for the same cooling capacity so it lowers bills even when tonnage stays constant.
Does altitude matter
Yes for combustion equipment and for some air-cooled heat pumps because air density changes with elevation. Capacity ratings usually assume standard conditions. Check the engineering data for correction factors if your site sits at high elevation.
How to use the BTU to tons converter on this page
Type a value in any field. The other two update instantly. Enter BTU/h from a label and read tons. Enter tons from a conversation and read BTU/h. Pick watts or kilowatts if you want the electrical equivalent. Keep decimals or round to halves when you size home equipment.
Pro tips for faster decisions
- Focus on cooling capacity, not unit size or brand hype.
- Use the quick table above to sanity-check quotes.
- Convert to kW when you compare electrical infrastructure.
- Remember that duct design and airflow matter as much as nameplate tonnage.
Worked mini-scenarios
Restaurant kitchen retrofit
The room load jumped after adding a new fryer bank. The sheet says an extra 36,000 BTU/h. Divide by 12,000 and you get 3 tons. The rooftop unit needs at least three more tons of sensible capacity at the expected return air temperature. The existing electrical feeder supports the added kW since 36,000 BTU/h equals about 10.55 kW.
Server closet with split AC
The UPS, switches, and servers dissipate about 7.5 kW. Multiply by 3.412142 to get 25,591 BTU/h. That equals 2.13 tons. Round up to a 2.5-ton system for headroom and better summer performance.
Home office upgrade
A quiet ductless unit rated 9,000 BTU/h sits in a space that warms fast in the afternoon. Converting shows 0.75 ton. After reinsulating the attic the load dropped and comfort improved without changing equipment. Right-sizing and building envelope upgrades work hand in hand.
Cheat-sheet formulas
- Tons from BTU/h:
T = Q / 12,000 - BTU/h from tons:
Q = 12,000 × T - kW from tons:
PkW = 3.516852842 × T - Tons from kW:
T = PkW / 3.516852842
Glossary at a glance
- BTU — unit of heat energy.
- BTU/h — heat transfer rate. This is the capacity number used for air conditioners.
- Ton of refrigeration (TR) — 12,000 BTU/h by definition.
- kW — SI unit of power equal to 1,000 watts.
- EER / SEER — energy efficiency indicators for cooling equipment.
Points To Remember
- The BTU to tons converter relies on one fixed fact: 1 ton = 12,000 BTU/h.
- Translate to kW with 1 BTU/h = 0.29307107 W for electrical checks.
- Right-size equipment to the building load for comfort and savings.
You now know how to turn BTU into tons and tons back into BTU/h without fuss. Keep the 12,000 constant in your pocket. Use the quick table for sanity checks. Match capacity to the true cooling load then verify electrical service with the kW equivalent. Your next quote will make sense and your space will feel right.
