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R-290 PT Chart: Pressure-Temperature Table and Lookup

Last reviewed October 2026

R-290 PT Chart

Quick Answer

At 40 °F, R-290 is at 63.9 psig at sea level. Set your elevation in the lookup if you are well above sea level.

R-290 pressure and temperature

Elevation

Saturation temperature°F

63.9psig

R-290 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-290 pressure-temperature chart · GreenCalculus · greencalculus.com/data/r-290-pt-chart/

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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	1.4
-39	1.8
-38	2.2
-37	2.6
-36	3.0
-35	3.4
-34	3.9
-33	4.3
-32	4.8
-31	5.2
-30	5.7
-29	6.1
-28	6.6
-27	7.1
-26	7.6
-25	8.1
-24	8.6
-23	9.1
-22	9.6
-21	10.2
-20	10.7
-19	11.3
-18	11.8
-17	12.4
-16	13.0
-15	13.6
-14	14.2
-13	14.8
-12	15.4
-11	16.1
-10	16.7
-9	17.4
-8	18.0
-7	18.7
-6	19.4
-5	20.1
-4	20.8
-3	21.5
-2	22.2
-1	22.9
0	23.7
1	24.5
2	25.2
3	26.0
4	26.8
5	27.6
6	28.4
7	29.2
8	30.1
9	30.9
10	31.8
11	32.7
12	33.6
13	34.5
14	35.4
15	36.3
16	37.2
17	38.2
18	39.2
19	40.1
20	41.1
21	42.1
22	43.2
23	44.2
24	45.2
25	46.3
26	47.4
27	48.5
28	49.6
29	50.7
30	51.8
31	53.0
32	54.1
33	55.3
34	56.5
35	57.7
36	58.9
37	60.1
38	61.4
39	62.7
40	63.9
41	65.2
42	66.5
43	67.9
44	69.2
45	70.6
46	72.0
47	73.4
48	74.8
49	76.2
50	77.6
51	79.1
52	80.6
53	82.1
54	83.6
55	85.1
56	86.7
57	88.2
58	89.8
59	91.4
60	93.0
61	94.7
62	96.3
63	98.0
64	99.7
65	101.4
66	103.1
67	104.9
68	106.6
69	108.4
70	110.2
71	112.0
72	113.9
73	115.7
74	117.6
75	119.5
76	121.4
77	123.4
78	125.4
79	127.3
80	129.3
81	131.4
82	133.4
83	135.5
84	137.6
85	139.7
86	141.8
87	143.9
88	146.1
89	148.3
90	150.5
91	152.8
92	155.0
93	157.3
94	159.6
95	161.9
96	164.3
97	166.7
98	169.1
99	171.5
100	173.9
101	176.4
102	178.9
103	181.4
104	183.9
105	186.5
106	189.1
107	191.7
108	194.3
109	197.0
110	199.6
111	202.4
112	205.1
113	207.8
114	210.6
115	213.4
116	216.3
117	219.1
118	222.0
119	224.9
120	227.8
121	230.8
122	233.8
123	236.8
124	239.9
125	242.9
126	246.0
127	249.1
128	252.3
129	255.5
130	258.7
131	261.9
132	265.2
133	268.5
134	271.8
135	275.1
136	278.5
137	281.9
138	285.4
139	288.8
140	292.3
141	295.8
142	299.4
143	303.0
144	306.6
145	310.2
146	313.9
147	317.6
148	321.4
149	325.1
150	328.9

R-290 is propane used as a refrigerant. This chart gives its saturation pressure at every whole degree from -40 to 150 °F, computed from the reference equation of state for propane and checked against NIST.

Checked

We compared every value with 1 published table from NIST. It agrees with this chart to within 0.01 psi at every temperature both cover, closer than a chart printed to one decimal place can show. How we checked

How to read an R-290 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 64 psig and the suction line is at 52 °F. On the saturation line, 64 psig is a saturation temperature of 40.0 °F. Superheat is 52 − 40.0 = 12.0 °F.

Subcooling. The liquid line gauge reads 174 psig and the liquid line is at 90 °F. On the saturation line, 174 psig is 100.0 °F. Subcooling is 100.0 − 90 = 10.0 °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-290 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 0.8 °F (0.4 °C)	off by 0.4 °F (0.2 °C)
At 5,000 ft, using a sea-level chart	reads high by 1.9 °F (1.1 °C)	reads low by 1.0 °F (0.6 °C)

Worked out from this chart. For R-290, 1 °F is about 1.3 psi at a 40 °F suction and 2.5 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-290 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-290 reads 63.9 psig at sea level and 66.4 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, the same basis as Arkema’s published 5,000 ft chart. Weather moves air pressure too, by much less.

About R-290

**GreenCalculus** MasterBrain data version 2026.284 · 1 factor from IPCC AR6 · key refrigerants.r_290 · each resolves at verify.greencalculus.com/‹key› with its source cell.
Type	Hydrocarbon (propane)
Composition	Single compound, propane (CH₃CH₂CH₃)
ASHRAE 34 safety class	A3: lower toxicity, higher flammability
GWP-100 (IPCC AR6)	0.02

Boiling point at 1 atm: -43.8 °F (-42.1 °C)
Critical temperature: 206.1 °F (96.7 °C)
Critical pressure: 616.6 psia (4,251 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.

R-290 is classed A3, higher flammability. Work on R-290 equipment only with the training and tools the equipment maker specifies.

How we checked these numbers

Every value is computed with CoolProp 8.0.0 from the reference equation of state for R-290 (Lemmon, McLinden and Wagner (2009), Journal of Chemical and Engineering Data 54(12)), 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 134 °F	190	-40 to 150 °F

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-290 PT chart

What is the pressure of R-290 at 40 °F?

At sea level, R-290 is at 63.9 psig at 40 °F. At 5,000 ft the same refrigerant reads 66.4 psig, because the gauge reads against thinner air.

What should my R-290 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-290 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 110.2 psig for R-290 at sea level. It shows refrigerant is present, not how much.

Does elevation change the R-290 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.

Is R-290 the same as propane?

R-290 is the ASHRAE refrigerant number for propane, so the pressure-temperature relationship on this page is that of propane. It is classed A3, higher flammability.

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_2900.02kg CO₂e per kg leakedIPCC AR6 IPCC AR6 WGI Ch 7 Table 7.SM.7 (propane GWP-100)AR6-100 · retrieved 17 May 2026

See every source and its licence

Cite this page

APA

GreenCalculus. (2026). R-290 PT Chart: Pressure-Temperature Table and Lookup. MasterBrain data edition v2026.284 (6 Nov 2026). https://greencalculus.com/data/r-290-pt-chart/

BibTeX

@misc{greencalculus_r_290_pt_chart_2026,
  author       = {{GreenCalculus}},
  title        = {R-290 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-290-pt-chart/}
}

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

R-290 PT Chart

How to read an R-290 PT chart

Superheat and subcooling: a worked example

How far off a reading can be

Gauge pressure and elevation

About R-290

How we checked these numbers

Questions about the R-290 PT chart

Other refrigerants

Version history

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