Calculator
Example data table
| Scenario | Key inputs | Recommended size | Storage volume |
|---|---|---|---|
| Footrest for a patio chair | Seat H 45 cm, D 48 cm, W 52 cm, Cushion 7 cm | W 44.2 cm, D 36.0 cm, H 43.0 cm | ~19.6 L |
| Shared ottoman between two seats | Seat W 55 cm, Seats 2, Gap 8 cm, Balanced factor 1.0 | W 102.6 cm, D 36.0 cm, H 43.0 cm | ~45.6 L |
| Storage ottoman for garden tools | Use storage, Seat H 46 cm, Cushion 6 cm, Frame 2 cm | W 49.0 cm, D 38.4 cm, H 44.0 cm | ~32.5 L |
Formula used
- Finished height: Ottoman Height = Seat Height + Height Offset, then clamped to a practical outdoor range.
- Depth baseline: Depth = Seat Depth × Use Factor × Outdoor Factor.
- Width baseline: Width = (Seat Width × Use Factor) × Seats Spanned + (Gap × (Seats−1)).
- Shape adjustment: Square uses max(Width, Depth). Round uses Diameter = max(Width, Depth).
- Fit to patio: If patio limits are entered, scale Width and Depth by the same factor to keep clearance on both sides.
- Internal storage (liters): (Inner W × Inner D × Inner H) ÷ 1000, where inner dimensions subtract frame thickness and lid/base allowances.
- Fabric area (m²): (Top area + Side area) × 1.10 ÷ 10,000 for waste and seams.
How to use this calculator
- Select your units, then choose the ottoman’s primary use.
- Enter your chair’s seat height, depth, and usable width.
- If sharing, set how many seats you want to span.
- Add cushion thickness and a small setback if desired.
- Optionally add patio space and walkway clearance targets.
- Click calculate to see size, storage, and material estimates.
- Use CSV or PDF exports to share with builders or suppliers.
Ergonomic height targets for outdoor seating
For most patio chairs, an ottoman feels best when the finished top sits slightly below the seat surface. A practical target is chair seat height minus 2 cm to 4 cm, which reduces ankle flex and keeps knees relaxed. When you plan occasional seating, match the seat height instead, and avoid thick cushions that push the top too high.
Depth and width ratios that avoid crowding
Depth typically ranges from 60% to 95% of chair seat depth, depending on use. Footrests can be shallower, while a shared ottoman or extra seat benefits from more depth for stability. Width can follow 75% to 100% of chair usable width per seat spanned, plus a small gap between seats. These ratios keep legs supported without blocking movement in tight garden layouts.
Clearance and patio fit rules for smooth traffic
In outdoor spaces, circulation matters as much as comfort. A clearance target of 45 cm to 60 cm is common for walk paths near chairs, planters, and doors. When you enter patio width and depth, the calculator scales the ottoman to preserve clearance on both sides. This reduces trip hazards and prevents the piece from feeling oversized on balconies.
Storage volume and weather-aware construction
Storage ottomans work best when internal height remains after subtracting cushion thickness, lid thickness, and base thickness. The calculator estimates internal volume in liters using inner dimensions reduced by frame thickness. For outdoor use, add drainage gaps, elevate the base, and select rot-resistant materials or sealed panels. A breathable liner also helps reduce condensation when nights cool quickly.
Material planning with foam and fabric estimates
Foam volume helps you compare cushion builds: a thicker cushion increases comfort but raises finished height and can reduce internal storage. Fabric area is estimated from top and side surface area with a waste allowance for seams and alignment. Use these figures to price outdoor fabrics, choose UV-resistant thread, and plan removable covers for easier washing.
| Inputs | Key settings | Typical outputs |
|---|---|---|
| Seat H 45 cm, D 48 cm, W 52 cm | Use: Footrest, Cushion: 7 cm, Clearance: 50 cm | W ~44 cm, D ~36 cm, H ~43 cm, Volume ~20 L |
| Seat H 46 cm, D 50 cm, W 55 cm | Use: Storage, Frame: 2 cm, Cushion: 6 cm | W ~50 cm, D ~40 cm, H ~44 cm, Volume ~33 L |
| Seat W 55 cm, Seats: 2, Gap: 8 cm | Use: Footrest, Factor: 1.0, Rectangle | W ~103 cm, D ~36 cm, H ~43 cm, Volume ~46 L |
FAQs
1) How do I measure chair seat height correctly?
Measure from the ground to the top of the seat cushion where you actually sit. If the cushion compresses a lot, subtract about 1–2 cm for a realistic sitting height.
2) What is the best ottoman height for a footrest?
Most people like the finished top about 2–4 cm lower than the chair seat. That position reduces ankle strain and feels natural for relaxed lounging outdoors.
3) Should I choose a square, rectangle, or round ottoman?
Rectangles fit narrow spaces and align with benches. Squares feel balanced and easy to center. Rounds soften corners and improve walk-around safety on compact patios.
4) How much clearance should I keep around the ottoman?
Use 45–60 cm as a practical walkway target in most gardens. Increase it near doors or grill areas, and reduce only when space is limited and traffic is light.
5) Why does cushion thickness change storage volume?
The calculator treats finished height as including the cushion. A thicker cushion increases comfort but reduces internal height once lid and base allowances are subtracted, lowering usable storage volume.
6) Can I span two seats with one ottoman?
Yes. Set “Seats spanned” to 2 and enter the gap between seats. The width scales across both seat widths plus the gap, giving a shared surface for lounging or trays.
7) Are the weight and fabric estimates precise?
They are planning estimates. Wood density, joinery, hardware, and fabric layout can vary. Use the numbers to compare options, then add a safety margin before purchasing materials.