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Design calculators
The Tools menu holds six standalone calculators - quick, single-element checks you can run without building a full model. Type a few numbers and the answer updates live, so they're handy for sizing a beam, a footing or a bolt before (or instead of) drawing anything.
Every calculator opens as a small dialog: inputs on the left, results on the right that recompute as you type. Most show a green OK / red OVER verdict with a utilisation number (demand ÷ capacity - under 1.00 passes, over 1.00 fails) and name the governing (worst) check at the top. A ⧉ Copy button puts the inputs and results on your clipboard as a tab-separated table you can paste into a spreadsheet or email.
Send a result into the report
The footing, site-classification, retaining-wall and wind calculators also have a ＋ Add to report button. It drops the result into the Design calculations section of the PDF report as a titled card, so a standalone check reaches the submitted package without re-typing. Unverified calculators carry a caution on the card and trip the report's PRELIMINARY banner until you sign them off.
First-pass tools - verify before professional use
These are transparent first-pass design aids built on simplified assumptions (noted in each dialog's footnote). Always confirm the result against the relevant Standard, a manufacturer catalogue and - for anything in the ground - the soil report before relying on it. The concrete and geotechnical calculators in particular skip detailing, load combinations and many real-world effects.
Section calculator
Works out the geometric properties (area, second moments of area, section moduli, radius of gyration, torsion constant) for a shape you describe by its dimensions - useful when a member isn't a standard catalogue size. See also the section library for ready-made catalogue sections.
- Tools → Section calculator…
- Pick a Shape: Rectangle, Circle, RHS (hollow box), CHS (pipe) or I-section.
- Type the dimensions (in mm) for that shape - the input rows change to match the shape.
- Read the properties on the right; a small outline preview of the shape is drawn above them.
- (Optional) Switch the SI (mm) / Imperial (in) toggle to display the results in either unit system.
- (Optional) ⧉ Copy the table, or ＋ Create model section to add this section to your model.
| Input (by shape) | Meaning |
|---|---|
| Rectangle | Width b, Depth d (mm) |
| Circle | Diameter (mm) |
| RHS (hollow box) | Width b, Depth d, Wall t (mm) |
| CHS (pipe) | Outer diameter, Wall t (mm) |
| I-section | Depth d, Flange width bf, Web tw, Flange tf (mm) |
| Output | Meaning |
|---|---|
| Area | Cross-sectional area |
| Mass (steel) | Self-weight per metre, assuming steel (7850 kg/m³) |
| Centroid | The shape's centre of area |
| Ixx / Iyy / Ixy | Second moments of area (bending stiffness about each axis) |
| Zx / Zy (approx) | Elastic section moduli |
| Sx / Sy (plastic) | Plastic section moduli |
| Shear area Asx / Asy | Effective area resisting shear on each axis |
| rx / ry | Radius of gyration (drives slenderness / buckling) |
| Principal I1 / I2 | Maxima/minima inertia on the principal axes |
| J | Torsion constant (exact for solid rectangle/circle and open I-sections; "approx" for hollow/arbitrary shapes) |
| Iw (warping) | Warping constant - the partner to J for lateral-torsional buckling; non-zero only for open sections |
Create model section
＋ Create model section saves the computed shape into your model's section list. If a member is selected when you click it, the new section is assigned to that member straight away; otherwise it's added to the list for you to assign later. The new section carries its area, inertias and self-weight, so design checks can use it.
RC slab calculator
A reinforced-concrete slab check to AS 3600: it verifies bending and minimum steel across a one-metre strip, punching shear where a column lands on the slab, and a span-to-depth deflection rule of thumb. Background on the concrete workflow is in the concrete guide.
- Tools → RC slab calculator…
- Enter the slab geometry, concrete and steel grades, the reinforcement you intend to provide, and the design moment and punching load.
- Choose the Support condition (simply supported, continuous or cantilever) - it sets the allowable span/depth ratio.
- Read the verdict at the top and the per-check rows; ⧉ Copy if needed.
| Input | Meaning |
|---|---|
| Effective depth d (mm) | Depth from the top to the centre of the tension steel |
| Overall thickness D (mm) | Total slab thickness |
| Cover to bar centroid (mm) | Distance from the face to the bar centre |
| f'c / fsy (MPa) | Concrete strength / steel yield strength |
| Provided Ast (mm²/m) | Reinforcement steel area you're providing, per metre width |
| Design moment M (kN·m/m)* | The bending demand per metre |
| Column a / b (mm) | Plan size of the supporting column (for punching) |
| Punching load N (kN)* | The load punching through the slab at the column |
| Span (m) | Slab span (for deflection) |
| Support condition | Simply supported / continuous / cantilever |
| Output | Meaning |
|---|---|
| φMu | Design bending capacity of the strip |
| Ast provided / min | Your steel vs the code minimum |
| Minimum steel | Utilisation - is there enough steel to satisfy the minimum |
| Bending M/φMu* | Bending utilisation |
| φVuo | Punching shear capacity at the column |
| Punching shear V/φVuo* | Punching utilisation |
| Span/depth L/d (actual / limit) | Deflection rule-of-thumb ratio vs its limit |
| Deflection | Deflection utilisation |
Provide the steel as designed
Enter the reinforcement you actually intend to provide in Ast - the calculator checks that amount, it does not size the bars for you. The deflection row is a deemed-to-comply span/depth check, not a calculated deflection.
RC beam calculator
Checks a single rectangular reinforced-concrete beam section to AS 3600 for bending (φMu) and the concrete contribution to shear (φVuc), against the moment and shear you enter.
- Tools → RC beam calculator…
- Enter the beam width and effective depth, the concrete/steel grades, and the tension (and any compression) steel areas.
- Enter the design moment M* and shear V*.
- Read φMu, the ductility flag and the shear capacity on the right.
| Input | Meaning |
|---|---|
| Width b (mm) | Beam width |
| Effective depth d (mm) | Top to centre of the tension steel |
| Compression-steel depth dsc (mm) | Top to the centre of any compression steel |
| f'c / fsy (MPa) | Concrete strength / steel yield strength |
| Tension steel Ast / comp. Asc (mm²) | Bottom (tension) and top (compression) bar areas |
| Design moment M (kN·m)* | Bending demand |
| Design shear V (kN)* | Shear demand |
| Output | Meaning |
|---|---|
| φMu | Design bending capacity |
| ku / φ | Neutral-axis depth ratio and the strength reduction factor; flags over-reinforced (ku > 0.36) when ductility isn't assured |
| Bending M/φMu* | Bending utilisation |
| φVuc | Concrete shear capacity (no stirrups) |
| Tensile steel ratio ρw | Tension reinforcement ratio |
| Shear V/φVuc* | Shear utilisation on the concrete alone |
Stirrups are not included
The shear check is the concrete contribution only (φVuc). If V* exceeds φVuc you must add shear reinforcement (stirrups, φVus) - this calculator does not design them. Watch the over-reinforced flag too: a ku above 0.36 means the section may fail without warning.
Pad footing calculator
A combined AS 3600 concrete and geotechnical bearing check for an isolated (pad) footing carrying a column with axial load and biaxial moment. It checks bearing pressure under the base, bending in both directions, one-way shear and punching shear.
- Tools → Pad footing calculator…
- Enter the column size, footing plan size and thickness, cover, material strengths and the ground's ultimate bearing q_ult.
- Enter the column load: axial N*, and moments M*x and M*y.
- Read the corner pressures, the governing check and the required steel.
| Input | Meaning |
|---|---|
| Column bx / by (mm) | Column plan dimensions |
| Footing Bx / By (m) | Footing plan dimensions |
| Thickness D (mm) | Footing depth |
| Cover to bar centroid (mm) | Cover to the bar centre |
| f'c / fsy (MPa) | Concrete / steel strengths |
| Ultimate bearing q_ult (kPa) | Soil ultimate bearing capacity (from the soil report) |
| Axial N (kN)* | Vertical load from the column |
| Moment Mx / My (kN·m) | Biaxial moments at the column base |
| Output | Meaning |
|---|---|
| Bearing pressures (corners) | Pressure under each of the four corners |
| qmax / qallow | Peak pressure vs the allowable |
| Bearing q/qallow* | Bearing utilisation |
| Effective depth d | Computed effective depth used for the RC checks |
| Ast required (x / y) | Reinforcement needed each way (with the minimum) |
| Bending M/φMu (x) and (y)* | Bending utilisation each way |
| One-way shear V/φVuc* | Beam-shear utilisation |
| Punching shear V/φVu* | Punching utilisation around the column |
Fill from selected support
If you've solved a model, you don't have to retype the column load. Select a single support node, then click ↧ Fill from selected support - it pulls the governing solved reaction at that node and writes N*, M*x and M*y into the form (and tells you which load combination governed). Solve the model first, or the button warns you there are no reactions.
Retaining wall calculator
A first-pass design for a cantilever retaining wall: earth pressure by the Rankine method, then stability (sliding, overturning, bearing) and AS 3600 bending design of the stem and heel.
- Tools → Retaining wall calculator…
- Enter the wall height and the stem, base and toe dimensions.
- Enter the soil and concrete unit weights, the active pressure coefficient Ka, material strengths, cover, the base friction angle and the allowable bearing.
- Read the stability utilisations and the stem/heel steel.
| Input | Meaning |
|---|---|
| Wall height H (m) | Retained height |
| Stem thickness base / top (mm) | Tapering stem wall thickness |
| Base width / thickness (m / mm) | Footing slab width and depth |
| Toe length (m) | Footing length in front of the stem |
| γ soil / concrete (kN/m³) | Unit weights |
| Active coefficient Ka | Rankine active earth-pressure coefficient |
| f'c / fsy (MPa) | Concrete / steel strengths |
| Cover to bar centroid (mm) | Cover to the bar centre |
| Base friction angle φ (deg) | Soil-to-base friction (drives sliding resistance) |
| Allowable bearing qallow (kPa) | Allowable ground bearing pressure |
| Output | Meaning |
|---|---|
| Active force Pa | Horizontal earth thrust and the height it acts at |
| Sliding Pa/Rslide | Sliding utilisation (thrust vs friction resistance) |
| Overturning Mot / Mr | Overturning vs restoring moment, and the utilisation |
| Eccentricity e | How far off-centre the base reaction sits |
| qmax / qmin | Bearing pressures under the base vs the allowable |
| Bearing qmax/qallow | Bearing utilisation |
| Stem M / Ast* | Stem moment and required steel, with utilisation |
| Heel M / Ast* | Heel moment and required steel, with utilisation |
Level backfill only, no surcharge
This is a deliberately simple first pass: it assumes level backfill with no surcharge and no soil cohesion, and it doesn't credit passive resistance at the toe. Account for surcharge loads, sloping backfill, drainage and passive resistance separately, and check detailing against the Standard and soil report.
Bolt & weld capacity
A quick AS 4100 reference for the capacity of a single bolt and a fillet weld. Unlike the other calculators it has no demand input and no pass/fail - it just reports capacities you can look up.
- Tools → Bolt & weld capacity…
- Choose the Bolt diameter and Bolt grade, and how many shear planes have threads intercepted vs excluded.
- Enter the Ply thickness / fup for the bearing check, and the Weld leg / length and weld metal strength fuw.
- Read the bolt and weld capacities.
| Input | Meaning |
|---|---|
| Bolt diameter (mm) | 12 / 16 / 20 / 24 / 30 / 36 |
| Bolt grade | 4.6 or 8.8 |
| Shear planes - threads in / out | Number of shear planes with threads in the plane vs excluded |
| Ply thickness / fup (mm / MPa) | Connected plate thickness and its tensile strength (for bearing) |
| Weld leg / length (mm) | Fillet weld leg size and run length |
| Weld metal fuw (MPa) | Weld consumable tensile strength |
| Output | Meaning |
|---|---|
| φVf (shear) | Design shear capacity of the bolt |
| φNtf (tension) | Design tension capacity of the bolt |
| φVb (ply bearing) | Design bearing capacity on the connected ply |
| Governing bolt shear | The lesser of φVf and φVb |
| φVw (total) | Design capacity of the whole weld run |
| φvw per mm | Weld capacity per millimetre of length |
Reference lookup, not a joint check
These are single-fastener capacities for quick reference. The full bolt-group, weld-group and plate joint checks - with actual demands and utilisation - live in the inspector's connection panels, not here. For steel member checks see design checks and international steel; for generating the loads that drive a model see load generators.