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Bearing Pressure Converter

Converts the units that actually appear on a geotechnical report: tons per square foot, kips per square foot, kg per square centimetre and kPa. Both kinds of ton are listed separately, because tsf means two different pressures depending on who wrote it.

1 tsf = 95.76 kPa

Value

From

Decimal places

Footing area, m2 (optional)

Factor of safety

Jump to a common conversion

Typical presumed bearing values, for a sanity check

Ground	kPa	tsf (short)	ksf	kg/cm2

Every row and chip is a live link you can bookmark or share.

Number line showing one ton per square foot short at 95.76 kPa, one kg per square centimetre at 98.07, one bar at 100, one atmosphere at 101.33 and one long ton per square foot at 107.25, a spread of twelve percent. — All five get called about 100 kPa in conversation. On a footing, the twelve percent between the ends is not a rounding difference.

How to use this tool

Pick a value and two units. The list carries the units that turn up in real foundation work rather than the process engineering set, so tons and kips per square foot sit alongside kPa and kg per square centimetre.

The two optional boxes turn a pressure into something you can act on. Give it a footing area and it returns the total load in kilonewtons and tonnes. Give it a factor of safety and it divides an ultimate value down to an allowable one.

The ton is the problem

Tons per square foot is the most common unit in North American foundation reports and it is ambiguous.

A short ton is 2000 pounds and gives 95.76 kPa per tsf. A long ton is 2240 pounds and gives 107.25 kPa. That is a twelve percent difference between two numbers written identically. American practice means the short ton, older British and Commonwealth work often meant the long one, and a scanned report from the 1970s will not tell you which.

The metric tonne per square metre is a third thing entirely and not a near miss. It is 9.81 kPa, roughly a tenth of either imperial version, because a tonne spread over a square metre is a far gentler pressure than a ton over a square foot. Anyone reading t/m2 as though it were tsf is out by a factor of ten.

Why so many units cluster near 100 kPa

The chart above is not a coincidence, it is history. Several measurement traditions independently landed on a unit sized to roughly one atmosphere, because that is a natural human scale for pressure.

One kg per square centimetre is 98.07 kPa. One bar is 100 by definition. One atmosphere is 101.325. One short tsf is 95.76. They are all within a few percent, which made them casually interchangeable in conversation and, unfortunately, in some calculations.

For a rough feel that is fine. For a footing it is not. A five percent error in bearing pressure carried through to a footing area is a five percent error in the area, which on a heavily loaded pad is a real quantity of concrete and a real change in settlement.

A worked check you can repeat on paper

Start from the pound force and the square foot, both exact. A pound force is 4.4482216152605 newtons and a square foot is 0.09290304 square metres, so one pound per square foot is 47.88025898 pascals.

Multiply by 1000 for a kip per square foot: 47.880 kPa. Multiply by 2000 for a short ton per square foot: 95.761 kPa. Multiply by 2240 for a long ton: 107.252 kPa. Every figure on this page comes from that one starting point.

Now kg per square centimetre. A kilogram force is 9.80665 newtons and a square centimetre is ten to the minus four square metres, so the answer is 98066.5 pascals, or 98.0665 kPa. Note it is a force per area despite looking like a mass per area, which is exactly why kN/m2 replaced it.

Mistakes that catch people out

Assuming tsf means the short ton. It usually does in North America and it did not always elsewhere. Twelve percent is worth one email to confirm.

Reading t/m2 as a ton per square foot. A factor of ten apart. The metric tonne per square metre is a small pressure, not a large one.

Treating kg/cm2 as a mass. It is a force per unit area, with gravity already inside it. That is the whole reason the profession moved to kPa.

Mixing ultimate and allowable. A bearing capacity from a Terzaghi calculation is ultimate and needs a factor of safety, usually between two and three. A presumed value from a code table is already allowable. Applying a factor twice wastes a great deal of concrete.

Forgetting that bearing pressure is rarely the governing check. On clays, settlement usually decides the footing size long before capacity does. Converting a number precisely does not make it the right number to design against.

Popular bearing pressure conversions

The conversions people look up most. Each opens the tool ready to go with its own address.

0.5 tsf to kPa 1 tsf to kPa 1.5 tsf to kPa 2 tsf to kPa 2.5 tsf to kPa 3 tsf to kPa 4 tsf to kPa 5 tsf to kPa 6 tsf to kPa 8 tsf to kPa 10 tsf to kPa 15 tsf to kPa 20 tsf to kPa 50 kPa to tsf 75 kPa to tsf 100 kPa to tsf 150 kPa to tsf 200 kPa to tsf 250 kPa to tsf 300 kPa to tsf 400 kPa to tsf 500 kPa to tsf 600 kPa to tsf 800 kPa to tsf 1000 kPa to tsf 1 ksf to kPa 2 ksf to kPa 3 ksf to kPa 4 ksf to kPa 5 ksf to kPa 6 ksf to kPa 8 ksf to kPa 10 ksf to kPa 15 ksf to kPa 20 ksf to kPa 50 kPa to ksf 100 kPa to ksf 150 kPa to ksf 200 kPa to ksf 300 kPa to ksf 400 kPa to ksf 500 kPa to ksf 1000 kPa to ksf 0.5 kg/cm2 to kPa 1 kg/cm2 to kPa 1.5 kg/cm2 to kPa 2 kg/cm2 to kPa 2.5 kg/cm2 to kPa 3 kg/cm2 to kPa 4 kg/cm2 to kPa 5 kg/cm2 to kPa 6 kg/cm2 to kPa 8 kg/cm2 to kPa 10 kg/cm2 to kPa 50 kPa to kg/cm2 100 kPa to kg/cm2 150 kPa to kg/cm2 200 kPa to kg/cm2 300 kPa to kg/cm2 400 kPa to kg/cm2 500 kPa to kg/cm2 600 kPa to kg/cm2 1000 kPa to kg/cm2 1 tsf to ksf 2 tsf to ksf 3 tsf to ksf 4 tsf to ksf 5 tsf to ksf 10 tsf to ksf 500 psf to kPa 1000 psf to kPa 2000 psf to kPa 3000 psf to kPa 4000 psf to kPa 5000 psf to kPa 50 kPa to psi 100 kPa to psi 200 kPa to psi 300 kPa to psi 500 kPa to psi 1000 kPa to psi 0.1 MPa to kPa 0.5 MPa to kPa 1 MPa to kPa 2 MPa to kPa 5 MPa to kPa 10 MPa to kPa 1 tsf long to kPa 2 tsf long to kPa 3 tsf long to kPa 5 tsf long to kPa 10 tsf long to kPa 1 t/m2 to kPa 5 t/m2 to kPa 10 t/m2 to kPa 20 t/m2 to kPa 50 t/m2 to kPa 100 t/m2 to kPa

How this was checked

Every factor was derived from the exact definitions of the pound force, the square foot, the kilogram force and the square centimetre rather than copied from a table. The pound per square foot came out at 47.88025898 Pa, the pound per square inch at 6894.757293 Pa and the kilogram per square centimetre at exactly 98066.5 Pa, all matching published values.

The two tons were checked separately and confirmed at 95.7605 and 107.2518 kPa, a ratio of exactly 2240 over 2000. Round tripping was run across every pair of the fourteen units, all 196 combinations, converting a value out and back with no failures.

The presumed bearing values in the table are indicative figures from common code tables, given so a converted result can be sanity checked against the kind of ground it came from. They are not design values and no code should be replaced by a table on a web page.

Related Calculators and Reference

Terzaghi Bearing Capacity Calculator for working out the ultimate capacity that these units express.
Isolated Footing Sizing Calculator for turning an allowable pressure into a pad size.
Consolidation Settlement Calculator for the check that usually governs on clay rather than capacity.
Pile Bearing Capacity Estimator for when a shallow footing will not do.
Pressure Unit Converter for fluid and process pressures rather than ground bearing.
Stress and Modulus Converter for structural material stresses in psi, ksi, MPa and GPa.
Pressure Converter: psi, bar, kPa, MPa, atm, mmHg and water head for everything that is not a foundation, with gauge and absolute counterparts.