Soil Sulfur Calculator
Garden sulfur to lower pH, with rate and bags from bed size.
What it does
High pH locks nutrients away from acid lovers. Sulfur feeds soil microbes that slowly acidify the bed, unlike lime which pushes the other way.
The tool above scales sulfur to area and drop. Five hundred square feet of sandy bed dropping one point needs 6 lb at 1.2 per hundred, or 1.2 bags. The metric match is 46 m2 toward 2.7 kg.
Soil texture sets the factor. Sandy ground moves with the base rate, clay needs half again as much for the same shift, and loam sits between.
Patience rules sulfur. Microbes convert it over warm months, so fall spreads read by spring, with retests before round two.
Plants pick sides. Blueberries, azaleas, and rhododendrons cheer acid beds, while lilacs sulk, so treat beds, not whole yards.
How to use
- Pick imperial (sq ft, lb) or metric (m2, kg).
- Enter bed area.
- Pick drop: 0.5 or 1.0.
- Pick soil: clay needs 1.5 times.
- Read sulfur first, then rate.
- Read bags, spread, and retest.
Formula
- area
- Bed area.
- drop
- pH points to drop: 0.5 or 1.0.
- soil
- Sandy or clay ground.
Metric uses 0.0586 kg per m2 per point for sandy beds with the same clay factor. Split large doses across seasons.
Worked example
Example: 500 sq ft, drop 1.0
Imperial defaults: 500 sq ft sandy bed dropping 1.0 pH. These are also the default values, so the page opens on this answer.
- Bed: 500 sq ft, sandy soil.
- Goal: drop pH by 1.0.
- Rate: 1.2 lb per 100 sq ft.
- Sulfur: 500 / 100 x 1.2 x 1.0 = 6 lb.
- Bags: 6 / 5 = 1.2 bags.
- Tool shows 6 lb, 1.2 lb per 100 sq ft, 1.2 bags (5 lb).
Reference table
| Bed | Drop 0.5 | Drop 1.0 |
|---|---|---|
| 250 sq ft | 1.5 lb | 3 lb |
| 500 sq ft | 3 lb | 6 lb |
| 1000 sq ft | 6 lb | 12 lb |
| 46 m2 | 1.3 kg | 2.7 kg |
Limits
- Estimate only. Tests rule treatment.
- Slow acting over warm months.
- Overshoots harm roots.
- Not a soil cleanup method.
Common mistakes
- Treating with no soil test.
- Dumping full doses at once.
- Expecting instant pH moves.
- Acidifying beds of lime lovers.
- Skipping the retest.
Try it yourself
Quick checks. Answers sit tucked under each question.
1000 sq ft sandy, drop 0.5?
1000 / 100 x 1.2 x 0.5 = 6 lb. Bags are 6 / 5 = 1.2 bags.
500 sq ft clay, drop 1.0?
500 / 100 x 1.2 x 1.0 x 1.5 = 9 lb. Bags are 9 / 5 = 1.8 bags.
Questions
Sulfur for 500 sq ft?
Multiply area units by rate by drop. Here 500 / 100 x 1.2 x 1.0 = 6 lb.
Rate per 100 sq ft?
Near 1.2 lb per 100 sq ft per point for sandy beds, times 1.5 for clay.
Test before treating?
Test first, since sulfur overshoots harm roots. Sandy soils move fast, clay resists.
How fast does pH fall?
Water it in and wait months. Sulfur needs warm microbes to convert, with retests guiding round two.
Which plants want acid?
Yes. Blueberries and azaleas love acid beds; lilacs and clematis do not.
Does this clean soil?
No. Contaminated soils need lab review.