By Evan Christensen · Owner, The Barn Door Hardware Store
Published August 7, 2024 · Updated May 2026
Evan has owned and operated The Barn Door Hardware Store since 2016. Track length is the single most common ordering mistake we see — almost always the result of sizing to the opening instead of the door. Getting this number right before ordering is the most impactful thing you can do to ensure the installation goes smoothly. He and the team are available 7 days a week at info@thebarndoorhardwarestore.com.
The one rule that governs all track length calculations
Track length is always based on door width — never opening width.
This is the rule that applies across every sliding door configuration. The door must be wider than the opening (to overlap and cover it), and the track must be long enough to accommodate the door in both its fully open and fully closed positions simultaneously. Sizing to the opening instead of the door is the most common ordering mistake we see — and it produces a track that's always too short.
Step 1: Determine door width first
Before calculating track length, you need the door width — which is not the same as the opening width. The door must overlap the wall on each side to fully cover the opening and provide edge coverage:
| Room type | Overlap per side | Door width formula |
|---|---|---|
| Standard rooms — hallway, pantry, living space | 2 in per side | Opening + 4 in |
| Bedrooms and bathrooms | 3 in per side | Opening + 6 in |
| Minimum functional overlap | 1/2 in per side | Opening + 1 in |
This door width is what every track length formula below is based on.
Single sliding door — track length formula
Track length = 2× door width
This applies to both single door and biparting setups (two doors on one track from opposite ends). For biparting, calculate total combined door panel width first, then double it.
Worked examples
| Opening width | Door width (standard) | Minimum track length |
|---|---|---|
| 30 in | 34 in | 68 in |
| 32 in | 36 in | 72 in |
| 36 in | 40 in | 80 in |
| 40 in | 44 in | 88 in |
| 48 in | 52 in | 104 in |
| 60 in | 64 in | 128 in |
For longer tracks, junction plates join two sections end-to-end to achieve any length. Kits requiring tracks over 7'6" ship as multiple sections with junction plates included. See our junction plate guide for installation detail.
Bypass track length formulas
Bypass configurations use different door width formulas from standard hardware, which affects track length. All bypass track length = 3× door width for a fully clear opening.
Single bypass — 2 doors on one shared track
| Roller type | Each door width | Track length |
|---|---|---|
| Standard rollers | (Opening + 10 in) ÷ 2 | 3× door width |
| Spoke wheel rollers | (Opening + 13 in) ÷ 2 | 3× door width |
Double bypass — 2 doors on parallel tracks
| Application | Each door width | Track length (per track) |
|---|---|---|
| Standard | (Opening + 6 in) ÷ 2 | 3× door width |
| Bedroom / bathroom | (Opening + 8 in) ÷ 2 | 3× door width |
Worked examples for a 60 in opening
| Configuration | Each door width | Track length |
|---|---|---|
| Single bypass (standard rollers) | (60 + 10) ÷ 2 = 35 in | 3 × 35 = 105 in |
| Single bypass (spoke wheel) | (60 + 13) ÷ 2 = 36.5 in | 3 × 36.5 = 109.5 in |
| Double bypass (standard) | (60 + 6) ÷ 2 = 33 in | 3 × 33 = 99 in (per track) |
For more detail on bypass configurations and how the formulas work, see our bypass measuring guide.
Bifold track length
Bifold track length is the most commonly miscalculated — because it's the only configuration where track length equals total door panel width rather than 2× door panel width.
Track length = total door panel width (not 2×)
Total panel width formulas (2-door bifold)
| Goal | Total panel width | Track length |
|---|---|---|
| Minimum coverage | Opening + 3 in | = Total panel width |
| Fully clear, asymmetrical | Opening + 6 in | = Total panel width |
| Fully clear, symmetrical (recommended) | Opening + 10 in | = Total panel width |
Worked example for a 36 in opening (symmetrical, fully clear)
- Total panel width = 36 + 10 = 46 in
- Track length = 46 in
- Each panel ≈ 23 in wide
For the full bifold sizing guide, see our 2-door bifold guide.
Track length quick reference
| Configuration | Door width | Track length |
|---|---|---|
| Single sliding | Opening + 4 in (standard) / + 6 in (bedroom) | 2× door width |
| Biparting (per door) | (Opening ÷ 2) + 2 in | 2× total combined width |
| Single bypass (standard rollers) | (Opening + 10 in) ÷ 2 | 3× door width |
| Single bypass (spoke wheel) | (Opening + 13 in) ÷ 2 | 3× door width |
| Double bypass (standard) | (Opening + 6 in) ÷ 2 | 3× door width (per track) |
| Bifold (symmetrical, clear) | (Opening + 10 in) ÷ 2 per panel | = Total panel width |
Want us to verify your track length before ordering?
Email us at info@thebarndoorhardwarestore.com with your opening width and configuration — we'll confirm the correct door width and track length before anything ships. For the full pre-order checklist covering all measurements, see our complete measuring guide. Available 7 days a week.
