How this instrument works
One kilogram-force per square centimetre is the pressure produced by a one-kilogram mass pressing down under standard gravity, spread over one square centimetre. Standard gravity is itself a fixed figure, 9.80665 m/s² by international agreement, so 1 kgf works out to exactly 9.80665 newtons and 1 kgf/cm² to exactly 98,066.5 pascals — a unit anchored to a defined constant rather than to any particular location's actual local gravity.
This unit carries an older name worth knowing: the technical atmosphere, symbol at, distinguished carefully from the standard atmosphere, symbol atm, which is fixed instead at exactly 101,325 pascals. The two are close enough to confuse and different enough to matter — a technical atmosphere is about 3.2 percent smaller than a standard one, a gap that has caused real errors on equipment rated in one unit and read in the other.
PSI, pounds per square inch, comes from an entirely separate imperial lineage — 6,894.757293168361 pascals exactly, derived from the pound-force and the inch. Dividing one defined pressure by the other gives this sheet's factor, 14.2233433071, an exact figure carried to ten decimal places rather than a measured approximation. kgf/cm² persists on equipment built to older metric-but-not-SI conventions: motorcycle and scooter tyre placards across much of Asia, boiler and compressor nameplates translated from German or Soviet engineering standards, and hydraulic press ratings that predate the pascal's widespread adoption.
- Enter a reading into the kgf/cm² (kgfcm2) field — 1 is preloaded as a baseline reference value.
- Read the PSI (psi) line beneath it; it recalculates on every keystroke to the full precision of the factor.
- For a tyre placard reading in kgf/cm², enter that figure directly to see the equivalent your gauge would need to show.
- Reversing direction, divide a PSI figure by 14.2233433071 to recover kgf/cm² — useful when translating a US-made gauge back to a foreign spec sheet.
Worked example — a European gauge on a US-built compressor
A vintage European air compressor carries a dial marked in kgf/cm², reading 1 at its lowest working mark, while the American-made hose fitting attached to it only lists a PSI rating. Enter 1 into kgf/cm² (kgfcm2) and PSI (psi) returns 14.2233433071 — noticeably below the 14.6959 PSI that one true standard atmosphere would give, a gap of roughly 3.2 percent that has real consequences on equipment rated close to its limit.
That distinction matters most at higher pressures, where the gap widens in absolute terms even though the percentage stays fixed: a boiler plate rated at 25 kgf/cm² converts to 355.583582678 PSI, not the 367.4 PSI you would get by mistakenly treating kgf/cm² as a standard atmosphere and multiplying by 14.6959 instead. On safety-rated equipment, that difference is exactly the kind of error worth catching before it reaches a pressure vessel.
Questions
Is 1 kgf/cm² the same as 1 standard atmosphere?
No, though the two are close enough to cause real confusion. One kgf/cm² — the technical atmosphere — is exactly 98,066.5 pascals, while one standard atmosphere is exactly 101,325 pascals, about 3.2 percent larger. In PSI terms that's the difference between 14.2233433071 and 14.6959 — small on a bicycle tyre, but worth checking carefully on any pressure-rated vessel or hydraulic system.
Why is this factor 14.2233433071 rather than a round number?
Because it is the exact ratio of two independently defined pressure units: 98,066.5 pascals for one kgf/cm², built from standard gravity 9.80665 m/s², divided by 6,894.757293168361 pascals for one PSI, built from the pound-force and the inch. Neither figure was chosen to divide evenly into the other, so their ratio runs to many decimal places; this sheet carries ten of them, far beyond what any mechanical gauge could resolve.
Where does kgf/cm² still show up today?
Mostly on equipment built to older metric-but-pre-SI engineering conventions: motorcycle and scooter tyre placards across much of Asia, hydraulic press and injection-moulding machine specifications translated from German, Japanese or Soviet-era standards, and boiler or compressor nameplates that predate the pascal's adoption as the standard SI pressure unit. It has been formally discouraged under SI since the 1970s but remains common in practice.
How is kgf/cm² different from bar?
Closely related but not identical — one bar is defined as exactly 100,000 pascals, a clean round figure chosen deliberately when the unit was introduced, while one kgf/cm² is 98,066.5 pascals, derived instead from standard gravity. The two differ by about 2 percent, close enough that some older equipment labels treat them as interchangeable, though a precise conversion should never assume they are equal.
Does altitude or local gravity change this conversion?
No — despite its gravity-based origin, a kgf/cm² is fixed using standard gravity, 9.80665 m/s² exactly, defined once by international agreement rather than measured wherever the gauge happens to sit. A gauge at sea level and one on a mountain plateau both read against the same defined unit, so this conversion factor never needs adjusting for location.
Is kgf/cm² an SI unit?
No. The SI system's pressure unit is the pascal, with the bar tolerated as a non-SI unit in some contexts; kgf/cm² belongs to an older, gravitational metric system that predates SI's adoption in 1960 and has been officially discouraged ever since, even though it remains printed on a great deal of equipment still in active service worldwide.