Weight & Payload Planner

Use this tool to organize information and identify questions. It cannot tell you that a build is safe to drive around a corner. The red map marker is a center of known, positioned component weights, not a measurement of your complete vehicle's center of gravity.

What is available?

A visitor draft is temporary. Closing the tab, reloading or leaving may lose it; the tool does not promise automatic browser recovery. A printed PDF preserves a report, not an editable saved plan. Sign in or check account availability if you want account storage.

Without signing in: make a standalone plan

1. Open the planner. Start with a blank plan and give it a useful name, such as “Trailer — travel loading.” Saving to an account and project imports remain unavailable.
2. Enter actual interior dimensions. Choose pounds/inches or kilograms/millimetres. Replace the starting 336 × 96 × 96 inches with measured usable space. Choose flat, V-shaped or rounded front geometry as appropriate.
3. Set the baseline and rating. Enter the measured baseline weight and document the tank levels, equipment and supplies included in that weighing. Enter manufacturer GVWR from the applicable label or documentation. A personal planning limit is optional.
4. Add a manual item. Enter its name, per-item weight, quantity, footprint length/width and height where known. Add materials, appliances, batteries, water contents, supplies or other loads you actually intend to carry. A manual planner item does not add a component to the shared registry or to a project.
5. Account for baseline items. If an item was already present in the baseline weighing, select “Already included in measured baseline.” This avoids adding its full weight again. Check the explanation below before using this with fluids.
6. Place items. Select a layer and mounting location, then choose “Place on layout” or enter coordinates. Drag a placed item to adjust it. Use the item list and layer filter to select overlapping items.
7. Explore loading. Add axle ratings and actual scale readings if available. Try water fill levels or alternate layouts, and capture loading scenarios while the tab is open. Review data gaps and the assumptions behind the map.
8. Keep a report. Click “Print plan,” review the new window and choose “Print / Save as PDF.” You can also sign in in the separate tab, return and click “Check sign-in” to save the current draft.

Undo/Redo helps with recent edits in the current session. It is not a backup after the tab closes. Starting a new blank plan discards the current draft after confirmation.

With an account: use project data and saved plans

1. Select Your project beside Saved plans. Choose Standalone plan, your project, or a project labeled “shared.” Selection associates the project with this plan; it does not automatically import components or replace the layout.
2. Prepare the project's measurements. The builder can open Edit Project and enable “Save a measured layout for builder tools.” Record interior dimensions, front shape, mounting allowances, baseline/GVWR and optional axle/scale information. Existing Build Specs platform length/width are separate from usable interior measurements.
3. Choose “Use project layout & readings.” This deliberately brings in the recorded settings. If placed items no longer fit, you can confirm that they should become unplaced. Recorded scale readings are not automatically confirmed for the current plan loading.
4. Bring in project components. Use the button in the Project components card. Current project weight and dimension overrides take priority over catalog values. Correct imported specifications in the project, then refresh/reopen the plan.
5. Add extra manual items and arrange the load. Imported values remain read-only, but placement, rotation, layer, mounting location, inclusion and baseline treatment can be adjusted. Add water contents separately when comparing tank fill levels.
6. Save plan. Give the plan a meaningful name. “Save plan” updates the current saved plan; “Save as new” makes a separate copy. Captured loading scenarios are retained with the saved plan.
7. Open the saved plan in 3D. Save current 2D changes first, then use the 3D button. The separate view edits the same saved plan. Save in 3D, return to 2D and reopen to view those changes.
8. Revisit and document. Select the plan and Open. Linked project weights and dimensions refresh from current authorized records when opening or saving. Recheck scale context after source or placement changes, then print a current report.

Working as a co-builder or assistant

Current accepted teammates can import shared components and layout measurements into their own private plans. The existing active-account and team verification rules apply. A pending invitation does not grant access. Only the builder changes project layout metadata in Edit Project; teammates can test alternatives in their own plans.

A teammate cannot open another account's private saved plan. If team access ends, linked project data and plans are no longer available through that membership. A PDF can be shared separately by its author, but this tool does not publish a saved plan for teammates.

Switching projects and working in multiple tabs

Changing the project removes previously imported items after confirmation; manual items remain. Standalone plan removes the project association. If you save from an older tab after another tab updated the plan, reopen the latest plan instead of overwriting it. Keep a report of any draft details you need before reopening.

Layout, baseline and payload

Length, width and height describe usable interior space. Height starts at 96 inches and is required. It supports vertical-clearance and 3D checks; payload totals come from weights, quantities and the baseline. The default height is not an actual measurement or a recommendation for your vehicle.

Front shape: Flat has no extension depth. Choosing V-shaped or Rounded enables depth. Length includes that extension. The rounded outline uses a half-ellipse approximation, and rectangular footprints must fit its usable shape. A cab or hood outside the usable body is not an interior extension.

Baseline weight is a fixed measured starting condition. Document the weighing date, installed equipment, people/supplies if present, and fuel/water levels. If those conditions change, establish a consistent new baseline or properly account for the changes. The planner does not automatically subtract removed equipment, consumed fluids or passengers from that number.

Manufacturer GVWR governs the overall entered manufacturer limit. A lower personal limit remains an additional target. A higher personal value does not override manufacturer GVWR. Combined axle ratings do not create or raise the manufacturer's GVWR.

Example: With a measured baseline of 4,500 lb and manufacturer GVWR of 14,000 lb, the arithmetic remaining amount is 9,500 lb before additional loads. Adding 2,000 lb gives a known total of 6,500 lb and remaining amount of 7,500 lb, assuming no unknown added weights. That arithmetic does not demonstrate acceptable axle, tire, hitch, braking or handling conditions.

The manufacturer label has distinct GVWR and axle-rating information. See 49 CFR 567.4 certification-label provisions; confirm the current rules applicable to your equipment and location.

Items, specifications and water

The Project components card is also where you add manual items and search the plan's item list. It is not a search of the entire shared registry. Selecting an item opens its editor. The inclusion checkbox controls whether that item participates in the selected loading; group-edit selection is separate.

Imported and manual values

Imported names, weights, quantities, status and dimensions come from the project. Weight, length, width and height are read-only in the planner. Use “Edit this project component,” correct its measurements, then bring in the components again or reopen/save. Do not substitute a guessed dimension merely to make a placement work.

If refreshed dimensions no longer fit, the item becomes unplaced so the plan can still open. Missing dimensions stay unknown. Manual rows have editable specifications. A real zero weight is different from an unknown value; empty water contents can legitimately weigh zero.

Whole project quantities up to 50 are represented as separate copies. Larger or fractional project quantities share one grouped footprint. A manual quantity also multiplies weight without creating separate physical boxes. Grouped rows are an accounting convenience, not a packing simulation. If separate placements matter, use suitable separate project assignments or manual rows, and avoid counting both versions.

Already included in measured baseline

Check this only when the row's weight was actually included in the baseline weighing. Its weight can still appear in the map's component balance, but it is not added to the total again. The checkbox does not deduct weight from the baseline or calculate a partial-weight difference.

Water fill scenarios

1. Add the dry tank/equipment if it is not already counted.
2. Add a separate manual row and choose “Water contents.” Enter capacity in US gallons or litres and choose fill percentage.
3. Use a documented baseline condition compatible with this extra water row. For empty-to-full comparisons, a measured empty-tank baseline avoids counting water twice.
4. Compare fill levels and capture the loading states you want to keep.

Water contents use the planner's 1 kg/L convention. For example, 20 US gallons at 50% is about 83.5 lb of water; the tank itself is separate. Fill changes the row's weight, not the displayed box height or a simulated liquid surface. If your baseline already contained water, changing a baseline-marked water row does not automatically change the fixed baseline—reconcile the weighing condition first.

Layers, mounting locations and positions

Layers are selection groups. Underbody, Floor, Interior 1–3, Walls, Roof 1–2 and Exterior help you select overlapping items. Add up to 20 custom layers per plan, such as “Under raised floor.” A layer does not automatically set elevation or mounting location.

Mounting location defines the permitted area. Configure measured exterior space under Layout & baseline when needed. Allocated rectangles and height clearances do not establish mounting strength, frame capacity, obstacle clearance or legal vehicle dimensions.

Coordinate origin: The rear/driver-side corner is X = 0, Y = 0. “From rear” increases toward the front; “From driver side” increases toward the passenger side. Positions describe the near rear/driver-side corner of the rotated rectangular footprint. Elevation is measured from the interior floor reference.

Move and rotate: Use Place on layout, drag the box, or enter coordinates. The 2D map offers a 3-inch snap and zoom controls. Rotation swaps the footprint's length/width direction; it does not change the recorded product dimensions. Arrow keys on a focused item move it in 3-inch steps. Group editing moves or rotates selected rows only when all resulting footprints fit.

Your cabinet/stove example: Put cabinets on Interior 1 and the stove on Interior 2. Filter Interior 2 to select the stove, or select it from the list to bring its outline above other items. Layer filtering changes what is drawn, not the included payload weight.

Raised floors: Tanks inside the body beneath a raised bedroom/bathroom floor are Interior items, not automatically Underbody. Use a custom lower-interior layer and set the bed/shower's elevation above them. Set true beneath-platform equipment to Underbody.

Roof vent beneath panels: Use separate Roof layers and measured elevations. Selecting roof-top mounting allocates at least a known component's height as vertical planning space; verify the actual roof structure and obstructions. Changing mounting location unplaces the item for deliberate repositioning.

Included exterior items count toward weight totals and the positioned-item center. Front/rear overhang weights contribute to the nearest end region. All of these displays remain simplified; they do not calculate hitch load or certify distribution.

Axles and scale readings

Add up to three axles. Number them front to rear and enter spindle positions measured from the rear of the usable body. Record each applicable GAWR from current vehicle/manufacturer information. Show axles on map changes their visibility only; their entered ratings remain available for comparisons.

The planner compares entered measured axle loads with entered GAWR. It does not divide total weight equally between axles, predict axle loads from the red marker, or calculate hitch/tongue load from placements. When axle and tongue readings are complete, a displayed combined reading depends on those readings being compatible measurements of the same loading.

Choose suspension type, enter actual readings, add the weighing date and describe conditions. “Readings match this loading” associates readings with the current planning data; it is not independent validation of the scale procedure or a safety approval. Moving loads or changing relevant source weights/footprints can mark that context stale. Reweigh as appropriate before relying on old readings.

Project layout imports always leave recorded readings unconfirmed for the receiving plan. Review what was weighed before confirming. Torsion/equalized suspension behavior and real axle load distribution need equipment-specific assessment; consult the Dexter applications manual and the manufacturer of your actual running gear.

Compare loading scenarios

The main planning selector includes either all checked items or installed items only. An unchecked item is excluded even when installed. Layer selection is independent of both controls.

1. Prepare a loading: water fill, included supplies, placements and status assumptions.
2. Enter a loading-scenario name, such as “Travel — half water,” and click Capture current loading.
3. Change the loading and capture another name. Up to ten snapshots can be kept; capturing an existing name replaces that snapshot.
4. Select a snapshot and Apply scenario. Inspect the result before saving or printing.

Applying a snapshot keeps the current layout dimensions, exterior spaces, units, suspension and overall rating settings. It does not restore an older manufacturer rating. The last retrieved project source values are retained rather than treating a historical catalog weight as authoritative; reopen or save to refresh them from the project. If snapshot footprints do not fit today's outline, the tool asks you to resolve that conflict.

Captured snapshots stay only in the current draft for visitors. Signed-in users must save the plan to retain them. “Save as new” is useful for a separate design alternative that should not replace the original plan.

Use the separate 3D view

1. Sign in, open or save a plan, and save any pending 2D edits.
2. Click Open saved plan in 3D. The view uses the same private saved plan and project-source rules.
3. Select a component from the list or by clicking a visible box. Choose a visible layer to isolate overlapping equipment.
4. In Top or Perspective, drag a component to move it horizontally at its current elevation. Drag empty space to orbit, or select Orbit view as the pointer action.
5. Use zoom buttons or scroll, Reset view, and Top/Side/Front/Perspective controls to inspect it. Side/Front views use coordinate fields for positioning; switch to Top or Perspective for dragging.
6. Set elevation in the editor when a tank, bed, cabinet or roof item sits above/below the floor. Keyboard arrows on the focused canvas move the selected placed item. Imported dimensions remain read-only.
7. Review unplaced items, unknown heights and overlap notices. Save plan, return to 2D, reopen it and review payload totals.

Known-height items are simplified solid boxes. Unknown heights appear as outlines; the renderer does not invent a product height. Overlap checks consider included placed items with known dimensions, including items hidden by the layer filter. A cabinet is drawn as a solid box, so an inset stove may produce an advisory overlap even though the real cabinet has a cutout.

This is not automatic packing, stacking-support analysis, roof/frame engineering, suspension simulation or rollover prediction. A visually clear layout does not demonstrate physical installation clearance or safe operation. The view does not calculate vertical center of gravity.

Review the data and keep a report

Understand the map and review panel

The Planning data review panel highlights missing weights, footprint dimensions, heights, placements, ratings and scale context. A complete set of entered values is still only a record of your inputs, not proof they are correct or that the build is safe.

Known total and remaining payload require a measured baseline. Unknown added weights make the known total incomplete, so remaining capacity is an upper bound. Unknown individual weights on already-weighed baseline items still make the component balance incomplete. Unplaced known weights count toward payload but do not appear in the map's positioned balance.

Density assumes weight is spread evenly across each visible footprint. The red marker and driver/passenger/end-region totals use known positioned component weights. They omit unknown/unplaced contributions and do not locate the baseline chassis mass unless you separately modeled it. Neither display is the complete vehicle's center of gravity.

Print or save a PDF

1. For a linked project plan, reopen or save to refresh project specifications, then verify the loading and measurements.
2. Choose the loading and visible layer you want documented. The map reflects that visible layer; total weight still covers the selected included loading.
3. Click Print plan. Allow the report window if your browser blocks it.
4. Check totals, data gaps, ratings/readings, the map and item table. The table distinguishes included/excluded and baseline-treated rows and shows dimensions, layer/mounting and coordinates.
5. Choose Print / Save as PDF and use your browser's printer or PDF destination. Keep it with the appropriate weighing notes and build documentation.

A printed report is a dated snapshot of the active draft/loading, not every captured scenario or a live specification feed. Its footer contains NPPSC's website, slogan, references and planning limitations. Share it as documentation without presenting it as a safety certificate.

Troubleshooting

References and current verification

Links reviewed for this guide on October 12, 2026. Availability does not establish that a document is the latest edition or applies to your specific vehicle. Recheck editions, current rules and manufacturer instructions before using them.

• NHTSA certification-label interpretation 001059GF — historical label guidance; not a current approval for your build.
• Current eCFR certification-label provisions, 49 CFR 567.4 — confirm applicability and the current text.
• Dexter axle/suspension applications manual — verify current equipment-specific documentation with the manufacturer.
• NHTSA load-securement guidance — review restraints and actual operating conditions.

Obtain current advice from the relevant manufacturers and qualified vehicle/trailer professionals when modifying a load-bearing or safety-critical system. No warning-free planner screen or printed report replaces that assessment.

NPPSC
Build it. Document it. Share what works.