Hatch Calculator + Formula, Examples & Applications

Use this hatch calculator to determine the exact force and stroke length your linear actuator needs to open a hatch, skylight, trap door, or boat hatch. Enter your hatch weight, hatch length, and mounting position — and the tool calculates the peak force across the full opening arc. This page includes the live calculator, the physics formula, worked examples, a full engineering explanation, and FAQs.

What Is This Calculator For?

This calculator solves the core engineering problem in any hatch or lid automation project — figuring out how much force your actuator actually needs. The answer isn't just the weight of the lid. It depends on where the actuator mounts, how far the lid opens, and how many actuators you're using. Get those wrong and you'll either burn out an undersized actuator or spend twice what you need to.

Simple Explanation

Think about opening a heavy cellar door with one finger. Push near the hinge and it's almost impossible. Push at the far edge and it swings open easily. That's the same physics this calculator is solving — where you push, how heavy the door is, and how far it needs to swing all determine how hard you need to push. The calculator runs those numbers automatically so you can pick the right actuator without the guesswork.

How to Use This Calculator

1. Enter the hatch weight in pounds — the total weight of the lid or panel.
2. Enter the hatch length — measured from the pivot (hinge) to the far edge.
3. Set the opening angle — most trap doors and skylights open to 90 degrees.
4. Adjust the actuator mounting position along the hatch. Watch the force requirement update in real time as you move it.
5. Set the number of actuators — using 2 cuts the force requirement per actuator in half.
6. Read the required force and stroke length from the results. Your actuator must exceed the force figure shown.

The Hatch Actuator Force Formula

The calculator uses torque physics evaluated across every degree of the opening arc from 0° to 90°. The peak force is what you size your actuator against.

Where: Weight = hatch weight in lbs  |  CG_Distance = distance from pivot to hatch centre of gravity  |  θ = hatch angle from horizontal  |  Mount_Distance = distance from pivot to actuator attachment point  |  actuator_angle = angle between actuator line of action and hatch surface.

The calculator evaluates this at every degree from 0° to 90° and reports the highest value — that peak is what your actuator must comfortably exceed.

Simple Example

Engineering Applications

Skylights and Roof Vents

Skylights are one of the most common hatch actuator applications — and one of the most demanding. The actuator has to work against gravity at the worst possible angle when the skylight is nearly horizontal. Mounting too close to the hinge is a common mistake that leads to undersized actuators failing early. Use this calculator to find the optimal mount position that balances force and stroke for your specific skylight dimensions. For exposed roof installations, always specify IP66-rated actuators.

Trap Doors and Cellar Hatches

Trap doors present a unique challenge — they're typically heavy, need to open fully to 90 degrees, and often have limited space underneath for the actuator body when closed. The closed length of the actuator (not just the stroke) matters here. The calculator outputs both the required stroke and the implied open and closed actuator lengths so you can verify physical fit before buying.

Boat Hatches and Marine Access Panels

Marine applications demand weatherproofing above everything else. The force calculation is identical to any other hatch — but the actuator selection needs to account for salt air, water ingress, and vibration. IP66 is the minimum rating for any exposed marine installation. Two actuators are common on wider boat hatches both to share the load and to keep the lid balanced during opening.

Solar Panel Tilt Mechanisms

Solar panel automation is a growing application for hatch-style actuator calculations. The panel weight and tilt angle directly determine force requirements, and panels often need to hold a precise intermediate angle rather than fully opening to 90°. The calculator handles any target angle — not just 90° — so you can size the actuator for the exact tilt position your solar tracking system requires.

Tonneau Covers and Truck Bed Lids

Automated tonneau covers need actuators sized for the full weight of the panel, often at awkward mounting geometries inside the truck bed rails. Available space for the closed actuator length is usually tight. Run the numbers through the calculator first — it's common to find that two smaller actuators fit the space constraints better than one large one, and the force split makes the per-actuator requirement very manageable.

Advanced Example — Two Actuators on a Heavy Skylight

Frequently Asked Questions