Payload is the number that quietly decides whether a van build works. It is not the same as cargo volume, and it runs out sooner than almost anyone expects, because a conversion consumes a large share of it before a single item of gear goes in. This calculator estimates what you have left, and where the weight you have added is sitting.
It does not collect anything, store anything, or require an account. The math runs in your browser.
Enter your door sticker payload to begin
Every figure below updates as you type.
How this calculator works
Remaining payload is simple arithmetic: your door sticker rating, minus the conversion weight you entered, minus everything in the zone fields. Water is converted at 8.34 pounds per gallon. Occupants are included because the door sticker rating covers occupants and cargo together, which is the single most common way builders overshoot without noticing.
The axle split is an estimate, not a measurement. Each zone is assigned a longitudinal position relative to the wheelbase, and the calculator resolves a static moment to distribute that zone's weight between the two axles. Zones behind the rear axle, which is where rear door storage and hitch carriers sit, take weight off the front axle rather than simply adding to the rear, and the estimate reflects that. The wheelbase figure changes with the platform you select, so a Sprinter 144 and a Sprinter 170 produce different splits for identical gear.
The height figure counts what share of your added load sits above the window line, using the zone you assigned it to. Overhead cabinets and roof loads count as high; everything else counts as low or mid. There is no single threshold at which a build becomes unsafe, so the calculator flags proportions rather than declaring a verdict.
What it cannot tell you
This tool cannot know your actual corner weights, your axle ratings, or how your specific conversion distributed its own mass. It estimates from position, and position is only part of the picture. A finished build should be weighed. A CAT scale at a truck stop will give you front axle, rear axle, and gross weight for a few dollars, and that measurement replaces every estimate here. Compare those figures against the GVWR and the front and rear GAWR figures printed on the same door label. If you are near any of them, the scale is the authority and this page is not.
Where the reference numbers come from
The payload ranges shown for each platform are the manufacturer's own published figures for cargo van configurations, linked below. They are ranges across trims, wheelbases, roof heights, and drivetrains, and they describe vehicles as delivered from the factory. They are shown for context only and are deliberately not used as defaults, because a converted van's usable payload is always lower than the factory figure and only the label on your specific vehicle is accurate. Ford states this directly: max payload varies by configuration, and the doorjamb label is the figure for a specific vehicle.
Sources: Mercedes-Benz Vans, Sprinter Cargo Van specifications; Ford, 2025 Transit Cargo Van capability; Ram, ProMaster capability. Figures were recorded in July 2026 and manufacturers revise them by model year.
Related reading
For where weight belongs once you know how much you have, read Van Storage Ideas by Zone. For the load ratings that govern what you can put on the roof, see Roof Racks & Exterior Carry. For garage systems that keep heavy items low, see Van Storage & Organization.
Storage hardware is usually the largest single line in a build's weight budget, so it is worth costing before you buy. Our guide to van storage drawers covers what a rigid drawer unit adds before you load anything into it, the Sprinter rear door storage guide covers the hinge limits that govern what can hang on the doors, and the cargo van storage guide compares bins, drawers, cabinets and racking side by side.