Calculator
Enter forklift geometry and steering limits to estimate turning radii and clearance needs. Values are planning-grade and should be verified with manufacturer data or field tests.
Example Data
Use this sample to see typical outputs. Replace with your forklift dimensions for planning.
| Parameter | Example value | Notes |
|---|---|---|
| Steering type | Rear-wheel steering | Common for counterbalance forklifts. |
| Wheelbase (L) | 1.65 m | Axle-to-axle distance along the truck centerline. |
| Max steer angle (δ) | 78° | Use the manufacturer value if available. |
| Track width (T) | 1.10 m | Measured at the reference axle wheel centers. |
| Front overhang (OF) | 0.45 m | Front axle to frontmost point of the truck body. |
| Front projection (P) | 0.20 m | Adds allowance for forks, attachments, or load projection. |
| Clearance per side (C) | 0.15 m | Extra safety space to keep off curbs, racks, or edges. |
Formula Used
This calculator uses a geometric bicycle model to estimate turning curvature, then expands to wheel and corner envelopes.
- Reference turning radius: R = L / tan(δ)
- Wheel radii (approx.): Rin = R − T/2, Rout = R + T/2
- Corner envelope radius (rectangular approximation): Rcorner = √(Rside2 + d2)
How to Use This Calculator
- Select the steering type that matches your forklift configuration.
- Choose the units you will use for all dimension inputs.
- Enter wheelbase, track width, and the maximum steer angle.
- Add overhangs and front projection to capture forks and load.
- Set clearance per side for a practical safety buffer.
- Click Calculate Turning Radius to view results above the form.
- Use Download CSV or Download PDF to share outputs.
Technical Article
1) Why Turning Radius Matters on Construction Sites
Forklifts frequently operate in confined laydown yards, near excavations, and inside temporary structures. A small difference in turning diameter can decide whether an aisle remains passable or becomes a collision point. Turning geometry also affects edge protection near drop-offs, because the rear swing and corner envelope may cross the intended travel line.
2) Input Data That Drives the Swept Envelope
The calculator focuses on wheelbase, maximum steering angle, and track width, then expands the path using overhang and front projection. In practice, wheelbase values around 1.4–2.2 m and steering angles near 70–85° are common for compact counterbalance units, while attachments and long loads can add 0.2–1.0 m of effective projection.
3) Reading the Radius and Diameter Results
The reference radius is the geometric centerline path for an idealized turn. Planning decisions should use the outside front corner radius, because it typically governs the minimum turning circle. The “turning diameter including clearance” adds a margin on both sides, supporting safer layout decisions when racks, barriers, or parked plant reduce available space.
4) Practical Aisle and Staging Guidance
For right-angle movements, combine turning diameter with operational needs: pallet placement tolerance, pedestrian separation, and spotter visibility. When space is tight, increase clearance per side to reflect site variability, tire scrub, and surface irregularities. Use the swept width estimate to check whether the inner path could clip corners, curbs, or stacked materials.
5) Verification, Documentation, and Reporting
Validate critical routes by running a slow test turn with cones at the outside envelope and measuring the observed radius. If measured values differ, adjust inputs until the reported outside corner radius matches the field result. Export CSV for design checks and PDF for method statements, daily briefings, and permit-to-work attachments.
FAQs
Turning radius is the distance from the turn center to a reference point on the forklift. Turning diameter is twice the governing radius, usually based on the outside front corner envelope.
Use the turning diameter including clearance for planning aisles, gateways, and rack approaches. It accounts for a practical buffer beyond the geometric envelope.
Increase “Front projection” to represent forks, clamps, booms, or load overhang. This expands the outside front corner radius and can significantly increase required turning space.
Compare the spec to the calculator’s outside front corner radius. If the spec is measured at a different point, adjust overhang/projection so the envelope aligns with manufacturer reporting.
Tire scrub, steering linkage limits, surface friction, load weight distribution, and operator technique can widen the swept path. Always add clearance and verify tight routes with a controlled field test.
Start with 0.10–0.30 m for controlled indoor work, and increase for rough surfaces, poor visibility, or mixed traffic. Site rules and risk assessments should govern the final allowance.
It is best for conventional front- or rear-steer geometry. Articulated and multi-directional units have different kinematics; use manufacturer swept-path data or specialized modeling for critical designs.