Isolated Column Footing Design

Gross bearing pressure under a biaxially eccentric column load, one-way and punching (two-way, with eccentric moment transfer) shear, Whitney-block flexure, and bar anchorage, for a single rectangular spread footing by ACI 318-08 Ch. 15.

ACI 318-08

Column & footing geometry

Column positionFounding depthDfft

Footing lengthLftFooting widthBft

Column dim. (L-dir)c1inColumn dim. (B-dir)c2in

ThicknessTinCoverin

Column offset, L-direLinColumn offset, B-direBin

Column loads (unfactored)

PDkipPLkipPEkip

Mx — bends the footing along L (ETABS M2 convention)

MxDkip·ftMxLkip·ftMxEkip·ft

My — bends the footing along B (ETABS M3 convention)

MyDkip·ftMyLkip·ftMyEkip·ft

Soil & bearing

Allowable bearingqaksfPedestal weightkip

Soil unit weightpcfConcrete unit weightpcf

Materials & reinforcement

f'cksifyksi

Bar sizeAnchorage

Everything you have entered is in the address bar, so the link reproduces this exact calculation.

d = 20.25 in · 8 checks · all pass

Plan view

Effective depth

20.25 in

Gross bearing demand

3.78 ksf

Governing ultimate load

408.0 kip

Governing DCR

0.94

Design checks

Check	Ref	Demand	Capacity	DCR	Governs	Status
Bearing (gross, service)	Geotech. allowable	3.8 ksf	4.0 ksf	0.94	Governing combo: D+L	PASS
One-way shear, L-dir	ACI §11.2.1	104.5 kip	199.6 kip	0.52	qu = 4.08 ksf (uniform, Pu governing combo: 1.2D+1.6L)	PASS
One-way shear, B-dir	ACI §11.2.1	104.5 kip	199.6 kip	0.52	qu = 4.08 ksf (uniform)	PASS
Punching (two-way) shear	ACI §11.11.2.1	366.5 kip	509.1 kip	0.72	Eq. 11-33 b0 = 153.0 in, position: int	PASS
Flexure, L-dir	ACI §15.4.2/10.3	368.5 kip.ft	468.8 kip.ft	0.79	#6 @ 10.2 in o.c. (12 bars)	PASS
Flexure, B-dir	ACI §15.4.2/10.3	368.5 kip.ft	468.8 kip.ft	0.79	#6 @ 10.2 in o.c. (12 bars)	PASS
Anchorage	ACI §12.5	16.4 in	117.0 in	0.14	Standard 90° hook, ##6 db = 0.750 in	PASS
Punching shear, eccentric transfer (interior)	ACI §11.11.7	122.2 psi	164.3 psi	0.74	v_direct = 118 psi + v_Mx = 4 + v_My = 0	PASS

L-direction

Vu = 104.5 kip, φVc = 199.6 kip

Mu = 368.5 kip.ft, φMn = 468.8 kip.ft

#6 @ 10.2 in o.c. (12 bars)

B-direction

Vu = 104.5 kip, φVc = 199.6 kip

Mu = 368.5 kip.ft, φMn = 468.8 kip.ft

#6 @ 10.2 in o.c. (12 bars)

Design checks

Check	Demand	Capacity	DCR	Status
Bearing (gross, service)	3.780 ksf	4.000 ksf	0.945	✓ OK
One-way shear, L-dir	104.550 kip	199.645 kip	0.524	✓ OK
One-way shear, B-dir	104.550 kip	199.645 kip	0.524	✓ OK
Punching (two-way) shear	366.547 kip	509.094 kip	0.720	✓ OK
Flexure, L-dir	368.475 kip·ft	468.841 kip·ft	0.786	✓ OK
Flexure, B-dir	368.475 kip·ft	468.841 kip·ft	0.786	✓ OK
Anchorage	16.432 in	117.000 in	0.140	✓ OK
Punching shear, eccentric transfer (interior)	122.168 psi	164.317 psi	0.743	✓ OK

Calculation

1Effective depth
$d = T - \text{cover} - d_b$
$d = 24.00 - 3.00 - 0.750 = 20.25$
$d$ 20.25 in
2Uniform ultimate soil pressure (governing axial load only)
$q_u = \frac{P_u}{L \cdot B}$
$q_u = \frac{408.0}{10.00 \times 10.00} = 4.08$
$q_u$ 4.08 ksf

Notes

All 8 design checks pass. Governing DCR = 0.94.

What this calculator does not check

One-way shear and flexure use the uniform net pressure qu = Pu/(BL) from the governing axial load alone, not the true biaxial eccentric distribution — a documented simplification for moderate moments, carried over from the source.
Eccentric punching-shear moment transfer (ACI §11.11.7) is automated for an interior column only; check an edge or corner column with a significant applied moment by hand.
No overturning or sliding (global stability) check — this is a bearing/shear/flexure design of the footing itself only.
No published worked example has been reproduced against this port; verification is internal cross-checks with the original tool's own engine, disclosed as such.

Results are for preliminary sizing and educational use. They are not a design and must be reviewed, verified and sealed by a licensed or registered engineer before being used in construction.

isolated-footing-design v1.0.0 · ACI 318-08 · input b37c230c87e3ee0d