Home
Data
R-134a PT Chart: Pressure-Temperature Table and Lookup

Last reviewed October 2026

R-134a PT Chart

Quick Answer

At 40 °F, R-134a is at 35.0 psig at sea level. Set your elevation in the lookup if you are well above sea level.

R-134a pressure and temperature

Elevation

Saturation temperature°F

35.0psig

R-134a at 40 °F, sea level

Gauge pressure assumes sea-level air (14.7 psia). Set your elevation if you are well above sea level: a gauge reads against the air around it.

R-134a pressure-temperature chart · GreenCalculus · greencalculus.com/data/r-134a-pt-chart/

Jump to

Gauge pressure at sea level, -40 to 150 °F. Below 0 psig the reading is a vacuum, in inches of mercury.

Temp (°F)	Pressure (psig)
-40	14.8 inHg vac
-39	14.4 inHg vac
-38	13.9 inHg vac
-37	13.4 inHg vac
-36	13.0 inHg vac
-35	12.5 inHg vac
-34	12.0 inHg vac
-33	11.4 inHg vac
-32	10.9 inHg vac
-31	10.4 inHg vac
-30	9.8 inHg vac
-29	9.3 inHg vac
-28	8.7 inHg vac
-27	8.1 inHg vac
-26	7.5 inHg vac
-25	6.9 inHg vac
-24	6.3 inHg vac
-23	5.7 inHg vac
-22	5.0 inHg vac
-21	4.3 inHg vac
-20	3.7 inHg vac
-19	3.0 inHg vac
-18	2.3 inHg vac
-17	1.5 inHg vac
-16	0.8 inHg vac
-15	0.1 inHg vac
-14	0.4
-13	0.7
-12	1.1
-11	1.5
-10	1.9
-9	2.4
-8	2.8
-7	3.2
-6	3.6
-5	4.1
-4	4.6
-3	5.0
-2	5.5
-1	6.0
0	6.5
1	7.0
2	7.5
3	8.0
4	8.5
5	9.1
6	9.6
7	10.2
8	10.8
9	11.3
10	11.9
11	12.5
12	13.1
13	13.8
14	14.4
15	15.0
16	15.7
17	16.4
18	17.0
19	17.7
20	18.4
21	19.1
22	19.9
23	20.6
24	21.3
25	22.1
26	22.9
27	23.7
28	24.5
29	25.3
30	26.1
31	26.9
32	27.8
33	28.6
34	29.5
35	30.4
36	31.3
37	32.2
38	33.1
39	34.1
40	35.0
41	36.0
42	37.0
43	38.0
44	39.0
45	40.1
46	41.1
47	42.2
48	43.2
49	44.3
50	45.4
51	46.6
52	47.7
53	48.9
54	50.0
55	51.2
56	52.4
57	53.6
58	54.9
59	56.1
60	57.4
61	58.7
62	60.0
63	61.3
64	62.7
65	64.0
66	65.4
67	66.8
68	68.2
69	69.7
70	71.1
71	72.6
72	74.1
73	75.6
74	77.1
75	78.7
76	80.2
77	81.8
78	83.4
79	85.0
80	86.7
81	88.4
82	90.0
83	91.8
84	93.5
85	95.2
86	97.0
87	98.8
88	100.6
89	102.5
90	104.3
91	106.2
92	108.1
93	110.0
94	112.0
95	113.9
96	115.9
97	118.0
98	120.0
99	122.1
100	124.2
101	126.3
102	128.4
103	130.6
104	132.7
105	135.0
106	137.2
107	139.5
108	141.7
109	144.0
110	146.4
111	148.7
112	151.1
113	153.5
114	156.0
115	158.4
116	160.9
117	163.4
118	166.0
119	168.6
120	171.2
121	173.8
122	176.5
123	179.1
124	181.8
125	184.6
126	187.4
127	190.1
128	193.0
129	195.8
130	198.7
131	201.6
132	204.6
133	207.5
134	210.6
135	213.6
136	216.7
137	219.7
138	222.9
139	226.0
140	229.2
141	232.4
142	235.7
143	239.0
144	242.3
145	245.7
146	249.0
147	252.5
148	255.9
149	259.4
150	262.9

R-134a is the HFC that replaced R-12 in car air-conditioning, and Chemours sells it as an automotive refrigerant. This chart gives its saturation pressure at every whole degree from -40 to 150 °F, computed from the reference equation of state and checked against NIST and Arkema.

Checked

We compared every value with 3 published tables from NIST and Arkema. They agree with this chart to within 0.08 psi at every temperature both cover. How we checked

How to read an R-134a PT chart

A pressure-temperature (PT) chart gives the pressure at which a refrigerant boils or condenses at each temperature: its saturation pressure. Where liquid and vapor are both present, as in an evaporator, a condenser or a cylinder, the pressure and the temperature are tied together, so a gauge reading tells you the temperature the refrigerant is boiling or condensing at.

The pressures are gauge pressure (psig) at sea level. Below 0 psig the refrigerant is under vacuum, and the chart shows inches of mercury instead. Switch the units above to °C, kPa or bar, and type any temperature or pressure into the lookup for a value between the rows.

Superheat and subcooling: a worked example

The lookup above does both calculations. Here is what it does, with example readings. They show the method only; they are not target pressures for any system.

Worked example

Superheat. The suction gauge reads 35 psig and the suction line is at 52 °F. On the saturation line, 35 psig is a saturation temperature of 40.0 °F. Superheat is 52 − 40.0 = 12.0 °F.

Subcooling. The liquid line gauge reads 124 psig and the liquid line is at 90 °F. On the saturation line, 124 psig is 99.9 °F. Subcooling is 99.9 − 90 = 9.9 °F.

Whether a superheat or subcooling figure is right for a system depends on that system. Compare with the manufacturer’s charging instructions.

How far off a reading can be

Superheat and subcooling are differences of a few degrees, so a small error in the pressure shows up in the answer. This table works out, from the R-134a chart itself, how far each common mistake moves the result.

Mistake	Superheat suction at 40 °F	Subcooling liquid at 100 °F
The gauge reads 1 psi off	off by 1.0 °F (0.6 °C)	off by 0.5 °F (0.3 °C)
At 5,000 ft, using a sea-level chart	reads high by 2.6 °F (1.4 °C)	reads low by 1.2 °F (0.7 °C)

Worked out from this chart. For R-134a, 1 °F is about 1.0 psi at a 40 °F suction and 2.1 psi at a 100 °F liquid line. At 5,000 ft a gauge reads 2.5 psi lower than at sea level for the same refrigerant pressure. R-134a is a single compound, so it has one column and no column mix-up.

Gauge pressure and elevation

A gauge reads the difference between the refrigerant’s pressure and the air around it. Air pressure falls with height, so at the same temperature a gauge reads higher up a mountain than at sea level. At 40 °F, R-134a reads 35.0 psig at sea level and 37.5 psig at 5,000 ft, where standard air pressure is 12.23 psia.

Enter your elevation in the lookup and the whole chart, CSV and printout switch to it. The tool uses the standard atmosphere, which is what Arkema’s 5,000 ft chart uses; our values match that chart to within 0.08 psi. Weather moves air pressure too, by much less.

About R-134a

**GreenCalculus** MasterBrain data version 2026.284 · 1 factor from IPCC AR6 · key refrigerants.r_134a · each resolves at verify.greencalculus.com/‹key› with its source cell.
Type	HFC, single compound
Composition	Single compound, 1,1,1,2-tetrafluoroethane (CH₂FCF₃)
ASHRAE 34 safety class	A1: lower toxicity, no flame propagation
GWP-100 (IPCC AR6)	1530

Boiling point at 1 atm: -14.9 °F (-26.1 °C)
Critical temperature: 213.9 °F (101.1 °C)
Critical pressure: 588.7 psia (4,059 kPa)

Boiling point and critical point are computed from the same equation of state as the chart. GWP is from our refrigerant GWP dataset; the refrigerant leakage calculator turns a leak into CO₂e.

Chemours describes R-134a as a non-ozone-depleting HFC that replaced R-12 and as the standard for mobile air-conditioning (Chemours). A car’s air-conditioning pressures depend on engine speed, airflow and the system, and a saturation table is not a charging target. Follow the vehicle maker’s service information.

How we checked these numbers

Every value is computed with CoolProp 8.0.0 from the reference equation of state for R-134a (Tillner-Roth and Baehr (1994), Journal of Physical and Chemical Reference Data 23(5)), as absolute pressure, then converted to gauge. Before publishing, we compared it with every independent table we could find:

Published table	Largest gap	Points compared	Range
NIST Chemistry WebBook, saturation properties (SRD 69)	0.00 psi at 136 °F	190	-40 to 150 °F
Arkema, Forane refrigerant pressure-temperature chart, PPC/SDC 05-2025 (NIST REFPROP 10)	0.05 psi at 95 °F	39	-40 to 150 °F
Arkema, Forane pressure-temperature chart, high elevation (5,000 ft) (NIST REFPROP 9) (at 5,000 ft)	0.08 psi at 60 °F	35	-20 to 150 °F

Gauge pressure at 5,000 ft: our absolute pressure less standard-atmosphere air pressure there (12.23 psia).

Checked 28 Oct 2026. A chart printed to one decimal place rounds by up to 0.05 psi.

The °C table is computed at whole degrees Celsius, not converted from the °F rows, and the two agree to within 0.01 psi.

Questions about the R-134a PT chart

What is the pressure of R-134a at 40 °F?

At sea level, R-134a is at 35.0 psig at 40 °F. At 5,000 ft the same refrigerant reads 37.5 psig, because the gauge reads against thinner air.

What should my R-134a pressure be?

The chart gives the saturation pressure at each temperature, not an operating target. Running pressures depend on the system, the load, the airflow and the charge. Compare with the manufacturer’s charging instructions, and use the chart to turn a gauge reading into a saturation temperature for superheat or subcooling.

What does R-134a read when the system is off?

When a system has been off long enough to even out, any part holding both liquid and vapor sits at the saturation pressure for its temperature. At 70 °F that is 71.1 psig for R-134a at sea level. It shows refrigerant is present, not how much.

Does elevation change the R-134a reading?

Yes. A gauge reads against the air around it, and air pressure falls with height. At 5,000 ft the standard atmosphere is 12.23 psia instead of 14.70, so every gauge reading is about 2.5 psi higher than at sea level for the same refrigerant temperature. Set your elevation in the lookup to correct the whole chart.

Can I use this chart to charge my car air-conditioning?

Not on its own. The chart gives the pressure at which R-134a boils at each temperature, which is useful for reading a gauge, but a car system’s pressures depend on engine speed, airflow and the system itself. Follow the vehicle maker’s service information.

Other refrigerants

Pressures are gauge at sea level; for blends, liquid (bubble) / vapor (dew). Safety classes are ASHRAE 34.

Version history

1.1.1 (29 October 2026): sources moved into a compact card at the end of the page, so they no longer break up the reading.
1.1 (28 October 2026): new section on how far off a reading can be, worked out for this refrigerant, and a note on how closely the published charts agree.
1.0.1 (28 October 2026): other refrigerants shown as cards, with each gas’s use, pressure at 40 °F, type and safety class.
1.0 (28 October 2026): first published.

Provenance

MasterBrain v2026.284

The factor this page used

Read from MasterBrain when this page was built. Each row names the published document and the cell the number came from, so you can check it against the original.

refrigerants.r_134a1,530kg CO₂e per kg leakedIPCC AR6 IPCC AR6 WGI Ch 7 Table 7.SM.7 (HFC-134a GWP-100). Aligned with existing gwp.HFC_134a.ar6_100.AR6-100 · retrieved 17 May 2026

See every source and its licence

Cite this page

APA

GreenCalculus. (2026). R-134a PT Chart: Pressure-Temperature Table and Lookup. MasterBrain data edition v2026.284 (6 Nov 2026). https://greencalculus.com/data/r-134a-pt-chart/

BibTeX

@misc{greencalculus_r_134a_pt_chart_2026,
  author       = {{GreenCalculus}},
  title        = {R-134a PT Chart: Pressure-Temperature Table and Lookup},
  year         = {2026},
  organization = {GreenCalculus},
  publisher    = {Numbers Publishing Pte. Ltd.},
  note         = {MasterBrain data edition v2026.284 (6 Nov 2026)},
  url          = {https://greencalculus.com/data/r-134a-pt-chart/}
}

Drawn from 21,133 factors across 294 source documents · edition v2026.284, updated 6 Nov 2026 · every source and its licence

R-134a PT Chart

How to read an R-134a PT chart

Superheat and subcooling: a worked example

How far off a reading can be

Gauge pressure and elevation

About R-134a

How we checked these numbers

Questions about the R-134a PT chart

Other refrigerants

Version history

Related on GreenCalculus