Allowable bearing capacity: The maximum pressure that can be applied to the soil from the foundation so that the two requirements are satisfied:
Ultimate bearing capacity: The minimum pressure that would cause the shear failure of the supporting soil immediately below and adjacent to the foundation.
For preliminary design purposes, BS 8004 [1] gives typical values of allowable bearing capacity which should result in an adequate factor of safety against shaer failure without accounting for the setllemenet criteria [2].
| Soil type | Bearing value (kPa) | Remarks |
| Dense gravel or dense sand and gravel | > 600 | Width of foundation not less than 1 m. Water table at least at the depth equal to the width of foundation, below base of foundation. |
| Dense dense gravel or medium dense sand and gravel | 200-600 | - |
| Loose gravel or loose sand and gravel | < 200 | - |
| Compact sand | > 300 | - |
| Medium dense sand | 100 - 300 | - |
| Very stiff boulder clays and hard clays | 300 - 600 | Susceptible to long term consolidation settelement |
| Stiff clays | 150 - 300 | - |
| Firm clays | 75 -150 | - |
| Soft clays and silts | < 75 | - |
| Very soft clays and silts | - | - |
Ultimate bearing capacity for shallow foundations according to Terzaghi
The utimate bearing capacity for shallow foundations can be calculated using the relation proposed by Terzaghi [3]:
and the net ultimate bearing capacity:
With the bearing capacity factors:
 | factor for surcharge |
 | factor for cohesion |
 | factor self-weight [4] |
 | factor self-weight [5] |
| B, L, D | Width, Length and Depth of foundation, |
 | cohesion, effective frinaction angle and effective unit weight |
In case of a rectangular foundation, the terms of the above relations should be multiplied by the respective shape factors as follows [6]:
In case the loads are not applied vertically, additional factors should be also considered for inclined loads.
