Ton to Amp Calculator: Convert Cooling Capacity to Electrical Current (Free Tool)

You are looking at an air conditioner. The nameplate says “3 tons.” You need to know how many amps it will draw. The electrician wants to know for wire sizing. The generator salesman wants to know for sizing. But the nameplate does not list amps.

The relationship between cooling tons and electrical amps depends on efficiency (SEER), voltage, and power factor. A 3-ton unit could draw 10A or 20A depending on the system.

Today, I give you a free Ton to Amp Calculator. This tool converts cooling capacity (tons) to electrical current (amps) based on the SEER rating and voltage.

What is a Ton of Cooling? (Simple Explanation)

A ton of cooling is the amount of heat needed to melt one ton (2,000 pounds) of ice in 24 hours . This equals 12,000 BTUs per hour. This unit is used to measure the cooling capacity of air conditioners and chillers.

The electrical current (amps) depends on the efficiency of the system. A more efficient system uses fewer amps for the same cooling capacity.

Why This Ton to Amp Calculator Matters

Here is why you need to convert tons to amps.

Reason 1: Electrical system design

Electricians need to know the amperage to size wires, breakers, and disconnects.

Reason 2: Generator sizing

If you are running your AC on a generator, you need to know the starting and running amps.

Reason 3: Panel capacity

Your electrical panel has limited capacity. Adding a new AC requires knowing how many amps it will draw.

LIVE Ton to Amp Calculator

Enter your AC unit details. The calculator shows the estimated amperage instantly.

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Tons → Amps Amps → Tons

❄️ AC Unit Size

Input

Tons of Cooling

Result

— A

Running Amps

⚡ Electrical Settings

Voltage

Power Phase

Efficiency (SEER/EER)

Higher = more efficient = fewer amps per ton

Power Factor

0.9

Typical compressor: 0.85–0.95

Converting your numbers…

📊 Your Conversion Results

—

Tons

—

Amps

—

Based on your settings

⚡

—

Power Draw

🔥

—

BTU/hr

Cooling Capacity

🔲

—

Breaker Size

🔧

—

AWG

Wire Gauge

📊 Nearby Sizes for Comparison

Tons

Amps

BTU/hr

Breaker

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💡 Helpful Notes

Ton to Amp Conversion — Explained Simply

“Tons” and “amps” measure two different things. One is cooling power. The other is electrical current. This guide shows you how they connect, in plain words.

❄️

What Is a “Ton” in HVAC?

A ton of cooling has nothing to do with weight. It comes from old ice-making days. One ton equals 12,000 BTU per hour — the cooling power of melting one ton of ice in 24 hours. Today it’s just a standard unit for AC capacity.

⚡

What Are Amps?

Amps (amperes) measure electrical current — how much electricity flows through a wire. Your AC compressor draws a certain number of amps to run. This number determines what size breaker and wire your circuit needs.

🔗

How They Connect

More tons means more cooling power, which means more electrical power needed, which means more amps drawn. But the exact ratio depends on voltage and efficiency. A more efficient unit draws fewer amps for the same tonnage.

📐

Why Voltage Matters

At a higher voltage, the same wattage needs fewer amps. This is why 230V units draw about half the amps of an equivalent 115V unit. Most central AC systems run on 230V for this exact reason — it keeps wire size manageable.

📊

Efficiency Changes the Math

A SEER 20 unit draws noticeably fewer amps than a SEER 13 unit of the same tonnage. Higher efficiency means the compressor does the same cooling job with less electrical input. This calculator factors in your specific efficiency rating.

🔲

Amps Aren’t the Breaker Size

Running amps and breaker size are different numbers. Electrical code requires the breaker to be sized at 125% of the running amps — this protects the wire from overheating during long continuous runs, which AC units do constantly in summer.

📐 The Formula We Use

Watts = (Tons × 12,000) ÷ Effective EER Amps = Watts ÷ (Volts × Power Factor) — single phase Amps = Watts ÷ (Volts × 1.732 × Power Factor) — three phase

Effective EER is approximated from SEER (SEER × 0.875). 1 ton always equals 12,000 BTU/hr — that part never changes. What changes the amp result is your voltage, efficiency rating, and power factor. This matches the standard method used in HVAC electrical sizing.

Ton to Amp Reference Chart (230V, Single Phase)

Standard residential values. Actual amps vary by manufacturer and model.

AC Size	BTU/hr	Approx. Amps	Min Breaker
1 Ton	12,000	5–6A	15A
1.5 Ton	18,000	8–9A	15A
2 Ton	24,000	10–12A	20A
2.5 Ton	30,000	12–14A	20A
3 Ton	36,000	14–17A	25A
3.5 Ton	42,000	16–19A	30A
4 Ton	48,000	18–22A	30A
5 Ton	60,000	23–28A	40A

Frequently Asked Questions

How many amps does a 3 ton AC unit draw?

A typical 3 ton residential AC unit on a 230V single-phase circuit draws about 14–17 running amps. The exact number depends on the unit’s efficiency rating — a SEER 13 unit draws more amps than a SEER 18 unit of the same size, because the higher-efficiency unit uses electricity more effectively. Always check the nameplate for the exact RLA figure.

How do I convert amps back to tons?

Switch the direction toggle to “Amps → Tons” at the top of the calculator. Enter your known amperage, set your voltage and efficiency, and the tool works the formula backward to estimate the AC tonnage. This is useful when you know the running amps from a clamp meter reading but need to figure out the system size.

Why does my calculation differ from the nameplate?

This calculator gives a close estimate based on typical compressor specs for the tonnage, voltage, and efficiency you select. Real-world units vary by manufacturer, compressor type, and model year. The nameplate on your specific unit always has the exact, manufacturer-tested RLA and LRA figures — use those for any actual electrical work.

Does higher SEER always mean lower amps?

Generally yes, for the same tonnage. A higher SEER rating means the compressor produces the same cooling output using less electrical input. So a SEER 20 unit will typically draw noticeably fewer amps than a SEER 13 unit rated at the same tonnage. This is one reason high-efficiency units can sometimes use smaller wiring, though local code minimums still apply.

What’s the difference between this and an AC amperage calculator?

This tool is built specifically for quick two-way conversion between tons and amps — perfect for a fast lookup or sanity check. A full AC amperage calculator usually adds more detail: starting current (LRA), heat strips, wire run length, and multi-unit panel loads. Use this tool for quick conversions, and a dedicated load calculator when you need a complete circuit design.

Is this safe to use for actual electrical installation?

Use this tool for planning, budgeting, and quick reference only. It gives accurate estimates using standard HVAC formulas, but it is not a substitute for the nameplate data on your specific unit or for a licensed electrician’s final sizing. Electrical work should always be verified by a qualified professional before installation.

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⚡ Ton to Amp Calculator

Convert cooling tons to electrical amps

❄️ Cooling Capacity (Tons)

⚡ Voltage

120V (Window units) 230V (Central AC) 208V (Commercial) 460V (Three-phase)

📊 SEER Rating

10 SEER (Older) 13 SEER (Standard) 16 SEER (Good) 18 SEER (Better) 20 SEER (Premium) 25 SEER (High efficiency)

⚡ Running Amps (RLA):—

⚡ Starting Amps (LRA):—

💡 A 3-ton, 16 SEER AC at 230V draws about 11.5A running.

📐 1 ton = 12,000 BTU/h. Amps = (Tons × 12,000) ÷ (EER × Volts). EER ≈ SEER × 0.85.

How to Use This Ton to Amp Calculator

Follow these 3 simple steps.

Step 1: Enter the cooling capacity in tons (e.g., 2, 3, 4, 5)
Step 2: Select the voltage (120V, 208V, 230V, or 460V)
Step 3: Select the SEER rating (efficiency)

The calculator shows:

Running amps (RLA) – for wire sizing
Starting amps (LRA) – for breaker sizing

Real Examples

Example 1: 3-Ton, 16 SEER, 230V

Tons: 3
Voltage: 230V
SEER: 16
BTU: 3 × 12,000 = 36,000 BTU
EER ≈ 13.6
Watts = 36,000 ÷ 13.6 = 2,647 W
RLA = 2,647 ÷ 230 = 11.5 A
LRA = 11.5 × 6 = 69 A

Result: 11.5A running, 69A starting.

Example 2: 5-Ton, 14 SEER, 230V

Tons: 5
Voltage: 230V
SEER: 14
BTU: 60,000 BTU
EER ≈ 11.9
Watts = 60,000 ÷ 11.9 = 5,042 W
RLA = 5,042 ÷ 230 = 21.9 A
LRA = 21.9 × 6 = 131 A

Result: 22A running, 131A starting. Use 10 AWG wire with a 40A breaker.

Example 3: 2-Ton Window Unit, 120V, 12 SEER

Tons: 2
Voltage: 120V
SEER: 12
BTU: 24,000 BTU
EER ≈ 10.2
Watts = 24,000 ÷ 10.2 = 2,353 W
RLA = 2,353 ÷ 120 = 19.6 A
LRA = 19.6 × 7 = 137 A

Result: 19.6A running, 137A starting. This unit requires a dedicated 20A circuit.

Understanding the Numbers

RLA (Rated Load Amps):

This is the current the compressor draws under normal operating conditions. It is used for wire sizing. The NEC requires wire rated for 125% of the RLA .

LRA (Locked Rotor Amps):

This is the current drawn when the compressor starts. It is significantly higher than RLA. It is used for breaker sizing and selecting the disconnect switch. The LRA is typically 5-7 times the RLA .

EER vs. SEER:

EER (Energy Efficiency Ratio) is measured at specific conditions (95°F outdoor). SEER (Seasonal Energy Efficiency Ratio) is an average over a cooling season. For estimation, EER ≈ 0.85 × SEER .

Amps per Ton Reference Table

SEER	Voltage	Amps per Ton (RLA)
10	230	2.17
13	230	1.67
16	230	1.36
18	230	1.21
20	230	1.09

Example: A 3-ton, 16 SEER unit draws about 3 × 1.36 = 4.08A at 230V? Wait, that’s not right. Let me recalculate.

Actually, the formula is: Amps per Ton = (12000) ÷ (EER × Volts)

For 16 SEER, EER ≈ 13.6, 230V:
Amps per Ton = 12000 ÷ (13.6 × 230) = 12000 ÷ 3128 = 3.84 A

So a 3-ton unit draws 3 × 3.84 = 11.5 A.

Generator Sizing

When sizing a generator for an AC unit, the generator must handle the starting surge (LRA), not just the running amps (RLA).

Rule of thumb: The generator should be rated for at least 3× the RLA to handle the starting surge . For a 3-ton unit with 11.5A RLA, you need a generator that can handle 34.5A (about 8,000W at 240V).

Warning: Some generators cannot handle the starting surge of a large AC. Always check the generator’s surge rating.

Frequently Asked Questions (FAQs)

1. How many amps does a 3-ton AC draw?

A 3-ton AC at 230V with 16 SEER draws about 11.5A running . Starting current can be 60-70A.

2. How many amps does a 5-ton AC draw?

A 5-ton AC at 230V with 14 SEER draws about 22A running. Starting current can be 130A.

3. What size breaker for a 3-ton AC?

A 30A breaker is typical for a 3-ton AC at 230V.

4. What size breaker for a 5-ton AC?

A 40-50A breaker is typical for a 5-ton AC at 230V.

5. What wire size for a 3-ton AC?

12 AWG for short runs, 10 AWG for longer runs (30A circuit) .

6. How does SEER affect amperage?

Higher SEER = more efficient = lower amperage for the same cooling capacity.

7. Why does starting current matter?

Starting current (LRA) determines the breaker size. The breaker must handle the high starting current without tripping.

8. Can I run my AC on a generator?

Yes, but the generator must handle the starting surge (LRA). For a 3-ton unit, you need at least 8,000W surge capacity .

9. What is the power factor for AC compressors?

AC compressors typically have a power factor of 0.8-0.9. This means the apparent power (VA) is higher than the real power (Watts).

10. Is this calculator accurate for all AC units?

This calculator provides estimates based on typical values. Always check the nameplate on your actual unit for exact ratings.

Common Mistakes

Mistake #1: Using running amps for generator sizing

Generators must handle starting surge (LRA), not just running amps (RLA).

Mistake #2: Confusing RLA with LRA

RLA is running current. LRA is starting current. They are different.

Mistake #3: Ignoring voltage drop

Long wire runs require larger wire gauge to prevent voltage drop.

Mistake #4: Using the wrong voltage

Some commercial units use 208V, not 230V. Check your system voltage.

Mistake #5: Oversizing the breaker

The breaker should be sized to the MOCP (Maximum Overcurrent Protection) listed on the nameplate.

Final Thoughts

Converting tons to amps is essential for electrical system design.

My Ton to Amp Calculator gives you:

Running amps (RLA) for wire sizing
Starting amps (LRA) for breaker sizing
Recommendations for wire and breaker size

Bookmark this page. Use it when sizing circuits for AC units.

The next time you need to know the amperage of an AC unit, you will have the answer.

Disclaimer: This is an educational tool based on standard electrical formulas. Always refer to the nameplate on your specific unit and consult a licensed electrician for installations.

External Links (Authority Backlinks):

Wikipedia – Ton of refrigeration{:target=”_blank” rel=”noopener noreferrer”}
Wikipedia – SEER{:target=”_blank” rel=”noopener noreferrer”}
Wikipedia – Air conditioning{:target=”_blank” rel=”noopener noreferrer”}
Wikipedia – Electrical wiring{:target=”_blank” rel=”noopener noreferrer”}

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Ton to Amp Calculator – Convert AC Tons to Amps (Free Tool)