How much lime do I need to raise soil pH by 1 point?

It depends on soil type. Sandy soil needs about 100g/m², loam about 200g/m², clay about 350g/m², and peat up to 500g/m². Clay and peat soils have higher buffering capacity and need more amendment to shift pH.

Is pelletised lime better than powdered?

Pelletised lime is easier to spread and less dusty, but slightly less effective weight-for-weight (about 80% compared to powdered). The calculator adjusts quantities accordingly. Pelletised is better for small garden applications; powdered for large areas.

How often can I apply lime or sulphur?

Avoid changing pH by more than 0.5 units at a time with lime, or 0.3 units with sulphur. Wait at least 3 months between applications and retest before adding more. Over-liming is difficult to reverse.

When is the best time to apply lime?

Autumn is ideal — lime has time to react over winter before spring planting. Avoid applying lime at the same time as manure or fertiliser, as it can cause nitrogen loss. Leave at least a month between lime and other amendments.

How do I lower soil pH for acid-loving plants?

Use flowers of sulphur at the rates shown by the calculator. For quicker results on small areas, use sulphur chips or acidifying fertilisers. Ericaceous compost and pine needle mulch also help maintain lower pH over time.

GardenCalcs

pH Amendment Calculator — Lime & Sulphur for Soil pH

Calculate how much lime or sulphur you need to adjust your soil pH.

Current pH

Current ph

Target pH

Target ph

Area

Total surface area to calculate for

Soil TypeYour soil type or condition

How We Calculate This

This calculator uses buffer capacity rates that vary by soil type to determine amendment quantities.

Lime rates (to raise pH by 1.0)

Sandy: 100 g/m²
Loam: 200 g/m²
Clay: 350 g/m²
Peat: 500 g/m²

Sulphur rates (to lower pH by 1.0)

Sandy: 25 g/m²
Loam: 50 g/m²
Clay: 80 g/m²
Peat: 100 g/m²

Applications are split to avoid changing pH by more than 0.5 (lime) or 0.3 (sulphur) units at a time.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.