Open a drawer in most modern kitchens and it glides out until you can see right to the back. Open one in an older kitchen and it may stop with a third of the contents still hidden under the worktop. The difference is the runner. This guide explains how full extension and partial extension runners work, where each makes sense and what to check before you buy kitchen drawer runners for a new build or a replacement.
What Does “Extension” Mean on a Drawer Runner?
Extension describes how far a drawer travels out of the cabinet compared with its own length. It is usually given as a fraction or a percentage:
- Partial extension (3/4): the drawer opens to about 75% of its depth, so the back quarter stays inside the cabinet.
- Partial extension (7/8): the drawer opens to roughly 87% of its depth, leaving only a small section hidden.
- Full extension: the drawer opens to its full depth, so the whole drawer box clears the front of the cabinet.
The figure refers to the drawer, not the runner itself, so a 500mm drawer on a 3/4 runner will leave around 125mm out of reach, while the same drawer on a full extension runner gives you access to every last millimetre.
How Full Extension Drawer Runners Work
Full extension drawer runners use three telescopic sections rather than two. The extra middle member lets the drawer travel the full length of the runner while staying supported at both ends. Most modern full extension designs also use ball bearings or rollers, which keep the movement smooth and quiet even when the drawer is heavily loaded.
Because the whole drawer comes out, you can see and reach everything without bending down and feeling around at the back. That matters most on deep base units, pan drawers and the bottom drawer of a stack, where the rear of a partial extension drawer can feel like a dark cave. Many full extension runners also come with soft close as standard, so the drawer is caught and pulled gently shut in the last few centimetres.
The trade-off is cost and space. Full extension runners have more parts, so they usually cost a little more, and a fully open drawer projects further into the room, which you need to allow for in tight galley kitchens or near an island.
How Partial Extension Drawer Runners Work
Partial extension drawer runners use two sections that slide against each other. With fewer moving parts they are simpler, lighter and often cheaper, which is why they are common on budget units, bedroom furniture and older kitchens.
A 3/4 runner suits shallow drawers where losing the back quarter does not matter, such as a cutlery or utensil drawer where most items sit towards the front. A 7/8 runner is a good middle ground: it keeps much of the access of a full extension design while staying compact. Our D Motion Runner is a 7/8 extension, soft close, undermount design rated to 25kg per pair, with tool-free fitting and ±4mm height and thickness adjustment.
The main limitation is access to the back of the drawer. On deep or heavily used drawers, the hidden section tends to become a place where things are forgotten.
Full Extension vs Partial Extension at a Glance
- Access: full extension gives 100% access; partial extension gives roughly 75% to 87%.
- Typical use: full extension suits pan drawers, deep base units and larders; partial extension suits shallow drawers and lighter furniture.
- Load: full extension runners are usually built for heavier loads; partial extension runners are often lighter duty.
- Space needed in front: full extension drawers project further into the room when open.
- Cost: partial extension runners are usually cheaper; full extension runners cost a little more but feel more premium.
Which Runner Should You Choose for Each Drawer?
The best answer is often a mix, matched to how each drawer is used:
- Pan and pot drawers: choose full extension and a high load rating. Heavy pans at the back of a drawer are exactly what partial extension hides.
- Bottom drawers: full extension saves you kneeling to reach the back, which makes bottom drawer runners one of the most worthwhile upgrades.
- Cutlery and utensil drawers: a 7/8 or even 3/4 runner is usually fine, as most items sit in the front tray.
- Drawers under a hob or sink: check clearances first. Full extension works well here, but pipework or hob fittings can limit the drawer depth you can use.
- Bedroom, office and utility furniture: partial extension is often enough for light contents, although full extension makes deep storage much easier to use.
If you are not sure what load each drawer will carry, our guide to drawer runner weight ratings explained shows how to estimate the weight and pick a rating with some headroom.
Mounting Type, Length and Space
Extension is only one part of the specification. Before you order runners for drawers, check:
- Mounting: side-mounted runners fix to the side of the drawer box and need a set gap each side, while undermount runners sit hidden beneath the drawer for a cleaner look.
- Length: runners are sold to suit drawer depth, so 400mm drawer runners suit a shallower cabinet, while 600mm drawer runners and longer suit deep units. Always measure the internal depth of the cabinet, not the outside.
- Drawer side thickness: some undermount runners only accept drawer sides up to a set thickness, such as 16mm.
- Clearance in front: make sure a fully extended drawer will not hit an island, a door, a radiator or a walkway.
- Opening style: push to open drawer runners work well with handleless fronts, but the mechanism must be designed for it.
Upgrading from Partial to Full Extension
Swapping old partial extension runners for full extension is one of the most noticeable upgrades in an older kitchen, and it is usually straightforward. Match the runner length to the drawer depth, check that the mounting type suits your drawer boxes and cabinet sides, and make sure the drawer box is strong enough for the heavier loads full extension invites. Old screw holes rarely line up exactly with new runners, so expect to drill fresh pilot holes. Our step-by-step guide on how to fit drawer runners properly walks through measuring, marking and adjusting.
Our Runners at a Glance
Aspin Collins stocks a range of runners for new builds and repairs:
- Ball Bearing Runners: full extension with soft close, rated up to 40kg, in lengths from 250mm to 550mm, so there are 250mm drawer runners for shallow units through to deep drawers.
- DTC Undermount Runners: full extension undermount runners, sold as a pair and rated up to 40kg, for heavy duty drawer runners that stay hidden.
- D Motion Runner: 7/8 extension, soft close and undermount, rated to 25kg per pair, a neat choice for lighter drawers.
You can compare every option, along with drawer packs, fixing brackets and push to open catches, in our Drawer Packs, Runners & Accessories collection. Whether you need a single soft close drawer runner pair or a full set of sliding runners for drawers, everything is delivered across the UK.
Frequently Asked Questions
1. Is full extension worth the extra cost?
For deep, heavy or frequently used drawers, yes. Being able to reach the back of every pan drawer and bottom drawer makes the kitchen easier to use every day, and the price difference per pair is usually small.
2. What does 3/4 extension mean on a drawer runner?
It means the drawer opens to about three quarters of its depth, so roughly a quarter of the drawer stays inside the cabinet when fully open.
3. Is a 7/8 extension runner the same as full extension?
No. A 7/8 runner opens the drawer to about 87% of its depth, leaving a small section hidden at the back. Full extension opens the drawer completely.
4. Can I swap partial extension runners for full extension ones?
Usually, yes. Match the runner length to the drawer depth, check the mounting type and drawer side thickness, and drill new pilot holes where the old ones do not line up.
5. Do full extension drawers need more space in front?
Yes. Because the whole drawer comes out, it projects further into the room. Check that it will clear islands, doors, radiators and walkways when fully open.
6. Are full extension runners always soft close?
Not always. Many modern full extension runners include soft close as standard, but check the product details, as some full extension runners close normally or use push to open instead.
