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More precision tools in the same niche.
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Boat Speed Calculator
The Boat Speed Calculator works out actual boat speed in knots, mph, and km/h from a distance and time you enter, and separately estimates the theoretical hull speed of a displacement-hull boat from its waterline length. It supports nautical miles, statute miles, and kilometres. Use it to check your average speed on a passage or to see the practical top speed a displacement hull can reach efficiently.
Boost Horsepower Calculator
The Boost Horsepower Calculator estimates how much horsepower a turbocharger or supercharger adds at a given boost pressure, starting from your engine's naturally aspirated baseline. It applies an adjustable efficiency factor to account for intercooling, heat, and tuning quality rather than assuming a perfect, lossless gain. Use it to sanity-check a boost target before committing to a turbo, injector, or fuel system upgrade.
Wheel Offset Calculator Logic
Backspacing (in) = (Width / 2) + (Offset mm / 25.4) + 0.5What Wheel Offset Actually Means
Offset (often labeled ET, from the German Einpresstiefe) is the distance in millimeters between a wheel's true centerline and its mounting face, the flat surface that bolts to the hub. Omni Calculator's wheel offset tool explains why this single number matters so much for fitment, it determines exactly how far the wheel and tire sit relative to the fender on one side and the suspension and brake components on the other, before you've even changed the tire itself.
This calculator covers both halves of that fitment question: converting a known offset into backspacing (the figure many older spec sheets and wheel shops still quote instead), and comparing a prospective new wheel and tire setup against what's currently mounted to see exactly how the fitment shifts.
Positive vs Negative Offset
Positive offset means the mounting face sits toward the outside (street side) of the wheel, pulling the wheel and tire inward toward the suspension, the setup most factory wheels use. The Motor Guy's guide to offset, backspacing, and fitment notes negative offset does the opposite, pushing the wheel outward toward or past the fender for a wider stance, with most factory positive offsets falling in the +15mm to +50mm range and aggressive negative setups running -12mm to -44mm.
How to Calculate Backspacing from Offset
Backspacing measures from the wheel's inner mounting edge to the back lip, a related but different figure than offset, and the two convert directly given the wheel's width. AmericanTrucks' wheel offset and backspacing tool uses Backspacing (in) = (Wheel Width ÷ 2) + (Offset in mm ÷ 25.4) + about 0.5 inches for typical rim flange thickness, the exact formula our calculator's Convert tab automates for a quick offset-to-backspacing lookup.
Comparing Two Wheel Setups: Poke and Tuck
The more useful real-world question is usually how a new wheel and tire combination compares to what's currently mounted. MiniWebTool's wheel offset comparison calculator runs exactly this side-by-side check, computing how much further out (poke) or further in (tuck) the new setup sits relative to the old one on both the fender side and the suspension side, since a wider wheel and a different offset can push or pull in either direction independently.
Will It Rub? Reading Your Clearance Numbers
Once you know how much a setup pokes or tucks, the next question is whether that change is safe. EngineerCalc's "will it rub" wheel offset tool uses a rough clearance guide worth keeping in mind, more than 10mm of remaining clearance is comfortable, 3 to 10mm is tight but usually workable, and under 3mm is very tight and may rub over bumps or at full steering lock, exactly the bands our calculator's clearance rating uses.
Remember these figures describe relative change, not your absolute remaining clearance, since that depends on how much room your specific fender and suspension already had before the swap. A setup that "pokes 8mm further out" could be perfectly safe on a car with generous stock clearance and genuinely rub on one that was already tight to begin with.
What "Poke" Actually Means
"Poke" specifically describes when the wheel and tire extend past the fender lip rather than sitting flush or tucked underneath it, a look achieved with negative offset and often a wider wheel. Wheel Fitment Calculator's explainer on poke notes it's purely a fitment outcome, not a separate spec you dial in directly, it's the visual result of whatever offset and width combination you've actually chosen. If your poke or tuck change is driven by a tire size swap rather than the wheel itself, our Tire Size Calculator handles the sidewall dimension side of that math.
Hub-Centric Bore and Common Mistakes
Offset and backspacing get most of the attention, but center bore matters just as much for a clean fit, if a wheel's bore is larger than the hub, it needs a hub-centric ring to seat properly and avoid extra vibration. Mechanics Calculator's complete offset and backspace fitment guide also flags the most common calculation mistake, forgetting that offset and width interact, changing only one number in isolation and assuming the other stays constant is how people end up surprised by rubbing they didn't calculate for. Always check both together, and confirm your specific tire size against our Tire Size Calculator before finalizing a fitment plan.
Frequently Asked Questions
Muhammad Shahbaz Siddiqui
Founder, TheCalculatorsHub
How I used the Wheel Offset Calculator to stop a reader from ordering wheels sight unseen
A reader emailed me in mid-2026 ready to order a set of 9.5-inch wide wheels at +12mm offset to replace his factory 8-inch, +40mm setup, chasing a more aggressive look without a clear sense of how big a change that actually was.
Running both setups through the calculator's Compare tab, the math showed his new wheels would sit about 47mm further outward on the fender side than his current setup, both the extra 1.5 inches of width and the 28mm offset drop pushing in the same direction. That's a large enough shift that the calculator's own guidance flags it for careful verification rather than a green light, per the general clearance framework EngineerCalc's wheel offset guide lays out, where under 3mm of actual remaining room is genuinely tight. Since his fenders had never been rolled and only had stock clearance to begin with, that 47mm shift was a real risk, not just an aggressive look, exactly the kind of case Wheel Fitment Calculator's guide to poke warns can rub without a physical test-fit first. He ended up choosing a milder +30mm offset instead, which the calculator showed would still poke about 29mm further than stock, meaningfully safer, and something worth test-fitting before ordering rather than assuming was fine either way.