Lift height is the maximum height to which a lift truck can raise its forks, set by its mast design. It varies widely by truck type, from low-lift pallet trucks to very tall narrow-aisle trucks.
Detailed Definition
Lift height, often called maximum fork height, is measured from the floor to the top of the forks at full mast extension. It is listed on the truck's specifications, and rated capacity is stated for a given lift height and load center. Related measurements include collapsed mast height, which limits passage through doors and trailers, free lift, which is how high the forks rise before the mast extends, and overall extended height, which must clear ceilings, lights and sprinklers. See forklift mast.
Matching lift height to racking
The top beam level of a pallet rack sets the minimum lift height a truck must reach, plus clearance to raise the pallet over the beam and set it down. Check overall extended height against the building's lowest overhead obstruction, such as sprinkler lines or lights, not just the roof deck. Collapsed height matters too if trucks must pass under doors or enter trailers. Narrow-aisle and turret trucks are generally used where storage is tallest. When a fleet serves several buildings, check each truck against the tallest rack and lowest door it will meet.
Capacity at height
Many trucks have a lower rated capacity at maximum lift height than at lower heights, because stability decreases as the load rises. The nameplate shows capacity for the mast, attachment and load center fitted. OSHA's powered industrial truck standard, 29 CFR 1910.178, requires manufacturer approval for modifications that affect capacity or safe operation, with nameplates updated to match.
- Check the nameplate before lifting near rated capacity at top levels.
- Recheck capacity after adding attachments such as side shifters or clamps.
- Train operators to travel with loads lowered.
Related Glossary Terms
Frequently Asked Questions
What is free lift on a forklift?
Free lift is the distance the forks can rise before the mast's inner section starts to extend above its lowered height. Trucks with full free lift can raise loads inside trailers, containers or low-clearance areas without the mast striking the ceiling. It is listed separately from maximum lift height on spec sheets. If you load trailers or work under mezzanines, check free lift and collapsed height as well as maximum lift height.
Why does a forklift's capacity drop at full lift height?
As a load is raised, the combined center of gravity of the truck and load rises, and the mast can deflect or tilt slightly, which reduces stability. Manufacturers therefore rate capacity for specific heights, and some trucks list reduced capacity near the top of the mast. The nameplate and capacity chart for your exact mast and attachment show the limits. Do not exceed them, even for a short lift.