Roller Conveyor Design Calculator
Roller spacing and diameter from product weight and dimensions.
About this calculator
Gravity and powered roller conveyors both hinge on one design rule: at least three rollers must sit under every product at all times so it can't rock, tip, or fall through a gap. This calculator starts there, taking your product's length in the direction of travel and dividing by three to get a target roller pitch, then snapping that number to the nearest standard spacing (25, 50, 75, 100, 150, or 200 mm) so you're specifying real, purchasable hardware. From the actual pitch it recomputes how many rollers sit under the product and divides the product weight across them to get load per roller — the number you check against a roller's rated capacity. It also sizes the roller face length as the product width plus 100 mm of side clearance, and estimates total rollers and maximum products on the conveyor, with a tighter spacing assumption when you flag the line as accumulation (back-to-back) rather than transport (gapped) mode. The calculator then branches by conveyor type.
For gravity conveyors, it derives the minimum slope from a friction coefficient of 0.04 (typical steel roller on carton) using tan(θ) = μ, adds a 50% safety margin so product reliably self-starts rather than stalling right at the theoretical angle, and reports the resulting drop over the conveyor's length plus an approximate rolling speed. For powered conveyors it instead computes the friction force from total load on the line and derives motor power at an assumed 85% drive efficiency. Because the friction coefficient and shape-factor assumptions are fixed defaults rather than inputs, treat the gravity slope and motor power outputs as solid starting points for equipment selection, not final specifications — verify against your actual product's coefficient of friction before committing to steel. Roller diameter feeds one output: Roller RPM, the rotational speed each roller turns at to produce the line speed (v × 60 / (π × D), assuming rolling without slip). It does not factor into pitch, load per roller, slope, or motor power — those depend on spacing and load, not on how big the tube is.
Inputs
Results
Roller pitch
200 mm
≈ 2 credit cards
How to Use This Calculator
- Enter the package or unit load weight and dimensions.
- Set roller diameter and center-to-center roller spacing.
- Input conveyor length and incline angle (0 for gravity or flat).
- Review the number of rollers needed, load per roller, and required drive force.
- Use the roller load to select appropriate roller capacity and bearing rating.
What each input means
- Product weight
- Weight of a single product or carton.
- Product length (travel dir)
- Product dimension in the direction of travel.
- Product width (across rollers)
- Product dimension perpendicular to travel.
- Conveyor length
- Total roller conveyor section length.
- Conveyor speed
- Line speed (for driven conveyors).
- Roller diameter
- Standard: 38, 50, 60, 76, 89 mm.
- Accumulation mode
- 0 = transport (gaps), 1 = accumulation (back-to-back).
- Gravity conveyor
- 0 = powered/driven, 1 = gravity (slope required).
What each result means
- Roller pitch
- Center-to-center distance between adjacent rollers.
- Rollers under product
- Number of rollers supporting each product simultaneously.
- Load per roller
- Maximum load on a single roller.
- Total rollers needed
- Total number of rollers in the conveyor section.
- Roller face length
- Between-frame roller length (product width + clearance).
- Max products on conveyor
- Maximum number of products the conveyor can hold.
- Required slope (gravity)
- Slope percentage for gravity operation (0 if driven).
- Slope angle (gravity)
- Slope angle in degrees for gravity operation.
- Drive motor power
- Motor power for driven roller conveyor (0 if gravity).
- Conveyor speed
- Operating or approximate gravity speed.
- Roller RPM
- Roller rotational speed at line speed — v × 60 / (π × roller diameter).
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does the calculator round my roller pitch to a standard spacing instead of using product length divided by three exactly?
It first computes a target pitch as productLengthMm / 3, then snaps that value to the nearest standard roller spacing from the set 25, 50, 75, 100, 150, or 200 mm, since those are the increments real roller conveyor frames are actually drilled for. Rollers-under-product is then recalculated at the actual standard pitch, which is why it can come out as 3 or more rather than exactly 3 depending on how the rounding falls.
What's the practical difference between accumulation mode and transport mode in this calculator?
Transport mode assumes a gap between products equal to half the product length (productSpacing = productLengthMm × 0.5), spreading fewer products across the conveyor, while accumulation mode sets that gap to zero so products can back up bumper-to-bumper. This directly changes maxProductsOnConveyor and, in driven mode, the total load the motor has to move.
Why is the gravity conveyor slope 50% steeper than the theoretical minimum?
The theoretical minimum slope is where tan(θ) just equals the friction coefficient (0.04), which is the knife-edge angle at which gravity barely overcomes friction. The calculator multiplies that slope by 1.5 as a safety margin (designSlopePct = slopePercent × 1.5) so product reliably starts rolling instead of stalling right at the calculated threshold, especially with cartons that are slightly heavier or stickier than assumed.
How is drive motor power calculated for a powered roller conveyor?
It multiplies the friction coefficient (0.04) by the total load on the conveyor and gravity to get friction force, then multiplies that by conveyor speed and divides by an assumed 85% drive efficiency: motorPowerW = (frictionCoeff × totalLoadKg × g × conveyorSpeedMps) / 0.85. Total load itself depends on whether you've selected accumulation mode, since that changes how many products are on the line at once.
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