Roundup, Montana · field elev 3,490 ft
Density Altitude at Roundup (KRPX)
From a field elevation of 3,490 ft, a typical July afternoon at Roundup (89 °F) raises density altitude to about 6,162 ft — solidly into the range where performance charts deserve a close read.
Typical density altitude by month
| Month | Avg temp °F | DA at avg temp | Afternoon high °F | DA on a typical afternoon |
|---|---|---|---|---|
| January | 25.1 | 2,058 ft | 37.2 | 2,886 ft |
| February | 27.8 | 2,245 ft | 40.7 | 3,121 ft |
| March | 36.3 | 2,825 ft | 50.6 | 3,774 ft |
| April | 44.9 | 3,400 ft | 59.9 | 4,374 ft |
| May | 54.2 | 4,008 ft | 69.1 | 4,954 ft |
| June | 63.1 | 4,577 ft | 78.3 | 5,522 ft ▲ |
| July | 71.2 | 5,085 ft | 88.9 | 6,162 ft ▲ |
| August | 69.5 | 4,979 ft | 87.9 | 6,102 ft ▲ |
| September | 59.6 | 4,354 ft | 76.9 | 5,436 ft ▲ |
| October | 46.3 | 3,492 ft | 60.9 | 4,437 ft |
| November | 34.2 | 2,683 ft | 46.6 | 3,512 ft |
| December | 25.7 | 2,099 ft | 37.2 | 2,886 ft |
▲ above 5,000 ft · ⚠ above 8,000 ft. These are planning references at standard pressure and dry air — afternoon humidity and low pressure both push the real number higher. Run today's values below.
Run today’s numbers for KRPX
DENSITY ALTITUDE caution
Field elevation 3,490 ft — the air behaves like 6,168 ft.
- PRESSURE ALT
- 3,492 ft
- ISA DEVIATION
- —
- RULE-OF-THUMB DA
- —
- AIR DENSITY INDEX
- —
- AIR DENSITY
- —
- WATER · GRAINS/LB
- —
For training and reference · verify with official sources and your POH before flight · no tool on this site renders a go / no-go judgment
Nearby Montana fields
- 80S — Lavina
Lavina · elev 3,512 ft
- 7S2 — Winnett
Winnett · elev 2,989 ft
- 8U0 — Ryegate
Ryegate · elev 3,689 ft
- KBIL — Billings Logan International
Billings · elev 3,662 ft
- 6S8 — Laurel Municipal
Laurel · elev 3,543 ft
- KLWT — Lewistown Municipal
Lewistown · elev 4,170 ft
- KHWQ — Wheatland County At Harlowton
Harlowton · elev 4,312 ft
- 6U7 — Hysham
Hysham · elev 2,624 ft
Frequently asked questions
How high does density altitude get at KRPX in summer?
On a typical July afternoon — around 89 °F at the nearest NOAA normals station — density altitude at Roundup reaches roughly 6,162 ft at standard pressure. Hotter-than-normal days, low pressure, and humidity all push it higher, so run the day's actual numbers before flying.
What is the density altitude at KRPX on an average day?
It swings with the seasons: from roughly 2,058 ft at the coldest month's average temperature to about 5,085 ft at the warmest month's — all from a constant field elevation of 3,490 ft. The month-by-month table above carries the full year.
What is the field elevation of Roundup?
3,490 ft MSL, from the FAA NASR airport record (28-day cycle effective 2026-08-06). The identifier is KRPX (ICAO) / RPX (FAA), in Roundup, Montana.