Paving Sand Calculator
Estimate the bedding sand needed beneath paving slabs, block paving, patios and paths: area, volume, weight, bags and optional bulk bags.
Results
Enter your project measurements to see your results.
What the paving sand calculator does
The sand bed beneath paving is thin, so it is easy to underestimate how much it weighs once spread across a whole patio. This tool multiplies the paved area by the bedding thickness, adds your waste allowance once, and converts the volume to weight using a density you can edit. It then divides by your bag size and rounds up.
Measuring the area
- Measure the length and width of the area to be paved, including any edge restraint bed if it takes sand.
- For L-shapes or curves, split the area into rectangles and run each one, then add the results.
- Measure the bedding thickness you plan to screed, not the depth of the paving units.
Bedding, sharp, building and jointing sand
These are not interchangeable. Sharp sand is coarse and commonly used for bedding layers or semi-dry mortar beds. Building sand is finer and mainly used in bricklaying mortar. Jointing sands and compounds fill the joints after laying. This calculator covers the bedding layer only; follow your paving manufacturer's specification for the material.
Worked metric example
A 5 m × 4 m patio is 20 m². At 30 mm bedding that is 0.6 m³, or 0.66 m³ with 10% waste. At an estimated 1,600 kg/m³ that weighs about 1,056 kg — 42.24 bags of 25 kg, so 43 bags, or two bulk bags if your supplier's bag holds 850 kg.
Worked imperial example
A 20 ft × 10 ft path is 200 sq ft. At 1 in thick that is 16.7 ft³. At an estimated 100 lb/ft³ it weighs about 1,667 lb before waste, or 34 bags of 50 lb.
Common mistakes
- Using the paving thickness rather than the sand bed thickness.
- Assuming dry and damp sand weigh the same — moisture adds weight.
- Adding waste twice, once to the area and again to the weight.
- Buying building sand when the specification calls for sharp sand.
When to get advice
The calculator estimates quantities only. Sub-base design, drainage, falls and the right bedding material depend on the site and paving product. For sub-base quantities see the MOT Type 1 calculator, and ask a qualified installer for driveways or heavily loaded areas.
Frequently asked questions
- How thick should a paving bedding layer be?
- It depends on the paving product, the laying method and the manufacturer's instructions. The thickness shortcuts here are examples only. Check the guidance for the slabs or blocks you are laying, then enter that thickness.
- Is bedding sand the same as sharp sand or building sand?
- No. Sharp sand is coarse and often used for bedding or in a mortar bed. Building (soft) sand is finer and mainly used for bricklaying mortar. Jointing sands and compounds fill the gaps between paving units. They behave differently and should not be swapped. Use the type your paving manufacturer or supplier specifies.
- Does this calculator work out jointing sand?
- No. It covers the bedding layer beneath the paving only. Jointing material depends on joint width, depth and product, and is not included.
- What density should I use?
- Use your supplier's figure if you have one. The starting value of 1,600 kg/m³ (100 lb/ft³) is an editable estimate, not a universal density. Sand weight varies with grading and especially with moisture.
- How many bulk bags of sand will I need?
- Enter the capacity your supplier states for its bulk bag. Bag sizes vary between merchants, so the calculator leaves this blank until you enter one, then divides the estimated weight by it and rounds up.