Ground Clearance Under Load Calculator

Estimate loaded rig clearance from unloaded ground clearance, payload, combined spring rate, front and rear load split, tire pressure deflection, skid plate drop, departure height, and suspension sag.

🚙Loaded rig presets

⚙Clearance, load, and suspension inputs

Unit system

Unloaded lowest ground clearance in

Measure the lowest fixed hard part before loading: differential, crossmember, tank guard, or frame bracket.

Added payload on this trip lb

Include people, water, fuel difference, food, tools, recovery gear, hitch cargo, and camper build cargo.

Front load split (%)

The rear split is calculated as the remaining percentage. Scale weights are better than guesses.

Rear load split (%)

Rear-heavy camper builds, cargo boxes, and tongue weight often push this higher.

Front combined spring rate lb/in

Use combined left plus right wheel rate if known. Higher rates sag less per added pound.

Rear combined spring rate lb/in

Leaf packs, airbags, helper springs, and coil conversions all change this effective rate.

Tire pressure deflection under load in

This is the extra loaded tire squat from your chosen pressure, not the whole sidewall height.

Skid plate or low accessory drop in

Enter how far a skid plate, tank guard, step bracket, hitch, or exhaust hangs below the unloaded reference point.

📐Departure clearance inputs

Wheelbase ft

Used for the center clearance ramp-over estimate and load-balance context.

Rear axle to lowest rear point ft

Measure horizontally from the rear axle centerline to hitch, bumper, spare tire, or rear skid contact point.

Unloaded rear departure height in

Use the lowest rear contact point, not the body sheet metal if a hitch or step hangs lower.

Trail bump compression allowance in

Subtract a reserve for dips, articulation, braking dive, and washboard suspension movement.

Minimum desired loaded clearance in

This target lets the calculator flag whether the loaded clearance is comfortable, tight, or below plan.

Lowest point axle bias

Choose where the measured low point sits. Rear differentials follow rear sag more than front sag.

Loaded low-point clearance

in after sag, tires, and skid drop

Suspension sag at low point

in effective sag from load split

Loaded departure angle

degrees from loaded rear height

Trail reserve after bump allowance

in above selected target

Calculation Breakdown

Enter your rig measurements and payload, then calculate.

📊Clearance quick grid

Sag

Payload divided by spring rate

Tire

Pressure deflection lowers frame

Skid

Accessory drop below low point

Depart

Rear height versus overhang

📘Reference tables

Loaded rig setup	Typical payload	Common rear split	Clearance watch point
Weekend camper van	500 to 900 lb	55% to 70%	Water tank, spare tire, rear step, and tank guard
Truck camper shell trip	900 to 1,600 lb	65% to 85%	Rear hitch, leaf-pack sag, differential, and spare carrier
Overland SUV cargo build	400 to 900 lb	50% to 70%	Skid plates, exhaust loop, fuel tank shield, and rocker steps
Teardrop or small trailer	300 to 800 lb	55% to 75%	Rear stabilizer jacks, axle tube, tank brackets, and receiver
Expedition truck build	1,200 to 2,500 lb	60% to 80%	Rear overhang, auxiliary tank, transfer case skid, and hitch

Combined spring rate	500 lb on axle	1,000 lb on axle	1,500 lb on axle
500 lb/in soft travel setup	1.00 in sag	2.00 in sag	3.00 in sag
800 lb/in common van rear	0.63 in sag	1.25 in sag	1.88 in sag
1,200 lb/in helper-supported axle	0.42 in sag	0.83 in sag	1.25 in sag
1,800 lb/in heavy truck pack	0.28 in sag	0.56 in sag	0.83 in sag

Tire pressure deflection	What it usually means	Clearance effect	When to remeasure
0.1 to 0.2 in	Firm street pressure with light added load	Small but real loss	After water or hitch cargo changes
0.3 to 0.5 in	Normal loaded camper pressure change	Can erase skid clearance margin	Before trail travel or ferry ramps
0.6 to 0.9 in	Aired-down tire or high sidewall squat	Major reduction at low hardware	Whenever pressure is changed off-road
1.0 in or more	Soft sand, snow, or intentionally low pressure	Plan crawl speed and obstacle line	After airing back up and reloading

Departure angle	Rear overhang feel	Loaded camping use	Risk note
25 degrees plus	Short rear overhang or high bumper	Usually comfortable on trail dips	Still check tow hitch and mud flaps
18 to 25 degrees	Moderate van, SUV, or truck camper	Good with careful line choice	Rear skid or hitch can touch first
12 to 18 degrees	Long van, rear box, or low hitch	Use caution on campsite entries	Driveways and ferry ramps need checks
Under 12 degrees	Long overhang with low rear hardware	Plan spotter support and slow angles	Departure contact is likely on dips

This calculator is a planning estimator. Real loaded clearance changes with bump stops, progressive springs, suspension geometry, tire construction, pressure, cargo position, water movement, and road angle.

🔧Comparison grid

Center low point

Average sag

Crossmembers, tanks, transfer-case guards, and exhaust pieces near the middle use a weighted blend of front and rear suspension sag.

Rear low point

Rear sag

Differentials, rear skids, hitch receivers, and spare carriers follow rear axle sag more closely when payload is behind the cabin.

Tire pressure

Deflection

Lower pressure can improve traction while lowering the whole rig. Re-enter tire squat after airing down or changing load range.

Departure

Angle

Rear overhang turns a small height loss into a large ramp risk, especially with hitch carriers, steps, and low stabilizers.

💡Clearance tips

Measure after the rig is actually loaded. Put water, passengers, camp food, tools, propane, bikes, and hitch cargo in their travel positions before you measure the lowest point.

Separate skid drop from suspension sag. A skid plate that hangs lower is a fixed loss, while sag and tire deflection change with payload, pressure, and cargo location.

Geometry

Not everyone fails at making their build look good… they fail at having good geometry. For example: you drop all that money on appliances, insulation and furnitures only to have your rig settle when you fill up water tank and pack in the kitchen. Now, the lowest point of your rig is nearer to the ground and what was once a smooth highway has become a scraping hazard.

Why Ground Clearance Matters

Ground clearance isn’t fixed. It is a moving number that decreases with each psi you let out of your tires and every pound you add. This change can be the difference between getting bent skid plates or getting home safely.

This leads us to a calculator which solves that math for you. After entering the unloaded dimensions of your truck and the payload you carry, you don’t need to estimate spring compression anylonger. Spring rate is at the heart of the equation. While most owners knows their payload capacity, they rarely know their spring stiffness. A soft suspension may feel comfortabley when driving around unloaded, but it sags almost two inches under a thousand pounds. Stiffer springs won’t move as much, but you’ll feel every bit of road shock through them. To strike a balance between these factors, you’ll notice that the tool asks you to enter combined front/rear rates.

Why? Camper loads aren’t evenly distributed. Sleeping platforms and water tanks typicaly rest behind the front axle. This shifts more load to the rear. Because of this rearward bias, your rear suspension sag further than the front. This affects your departure angle and places rear hardware out of range you believed was safe.

Tire deflection is another silent killer of clearances. Carrying a heavy load at street pressure or airing down for traction causes your sidewalls to flex inward. The sidewalls flex inward, lowering the wheel center and dropping frame. Half an inch lost from tire squat may seem trivial, but it multiplies with suspension sag. With your diff so close to the ground already, that half-inch difference can be the margin between clearing a bump or rubbing metal. The reference table on the page show this clearly and converts common pressure changes into inches of height.

Measure your lowest hard point unloaded and remember to add deflection. A lot of builders will measure their step or bumper, but neglect fuel tank guard or transfer case skid. It’s not usually the most obvious.

Let’s not forget departure angle either. Truck and van rear overhangs is long. As the rear suspension sags down under weight, that overhang drops vertically. Even just a little bit means a lot in terms of departure angle. This is critical for getting up onto ferry ramps and crucial for backing into campgrounds with steep driveways. The calculator find this value by adding the horizontal distance from your lowest point out back to your rear clearance loss. Spare tire carriers and hitch receivers sticking way out there mean a few inches of sag will be the difference between scraping across the top of a hill or high-centering on pavement.

There’s more to it in the real world. As your shocks compress and extend, their suspension geometry change. As progressive leaf springs sag, they get stiffer, drooping an inch at the end might not be as bad as the first inch. Trail riding includes dynamic forces different than the static estimate provided by the calculator. You hit washboard road, brake dive causes a load, and cornering roll adds a load that far exceeds your static weight. A good rule of thumb is to add a reserve allowance for bumps. That way, you’re never riding right up against the clearance margin.

Don’t go nuts trying to get as high up there as possible, but know yourself; know your limitations. When you know how far down your rig goes at max weight, then you can pull off with confidence. No more guessing what lines to follow. No more wondering about what is safe to cross. Your undercarriage stays in one piece. Your trip is stress free. You should of planned for it ahead of time. Know the numbers, respect the geometry.

Ground Clearance Under Load Calculator