Start with a soil test
Lime raises soil pH, but how much a lawn needs depends on both its current pH and how strongly the soil resists change, which varies a lot between sandy and clay soils. Only a lab test measures that, so this calculator works from your lab’s recommendation rather than guessing. Most state university extension services offer inexpensive soil tests for homeowners; the report tells you whether to lime and how much.
If your report recommends sulfur instead, your soil is too alkaline and needs its pH lowered. Lime would make that worse.
How to use this calculator
- Enter the recommendation from your soil test and choose its unit: pounds per 1,000 square feet, pounds per acre, or tons per acre.
- Enter your lawn area.
- Enter the product’s neutralizing value (calcium carbonate equivalent, or CCE) from the bag. If your lab’s recommendation assumes a different value than 100%, enter that too; your report usually says.
- Choose established lawn or new lawn. Established lawns get the amount split into applications of up to 50 pounds per 1,000 square feet.
The formulas
- Tons per acre to lb per 1,000 sq ft: multiply by 45.9
- Lb per acre to lb per 1,000 sq ft: divide by 43.56
- Adjusting for the product: product needed = recommendation × (CCE the lab assumed ÷ CCE of your product)
- Applications for an established lawn = product per 1,000 sq ft ÷ 50, rounded up
Worked example
Your soil test recommends 2 tons of lime per acre, based on 100% CCE. Your lawn is 5,000 square feet and you buy pelletized lime with a CCE of 90%, in 40-pound bags.
- 2 tons per acre × 45.9 = 91.8 lb per 1,000 sq ft
- Adjusted for the product: 91.8 × 100 ÷ 90 = 102 lb per 1,000 sq ft
- For the lawn: 102 × 5 = 510 pounds, or 13 bags of 40 pounds
- Because 102 is more than 50, an established lawn gets it in 3 applications of 34 lb per 1,000 sq ft (170 pounds each), spaced 1 to 6 months apart
Applying lime
- Use a spreader and make two passes at half the rate in different directions for even coverage.
- Fall and early spring are convenient times; lime can go down whenever the ground isn’t frozen or waterlogged.
- For a new lawn, work lime into the top few inches of soil before seeding or laying sod, where it acts fastest.
- Retest every 2 to 3 years. Lime works slowly, and a fresh test tells you when to add more.
Sources
- Virginia Cooperative Extension: Soil test note for lawns
- UConn Soil Nutrient Analysis Laboratory: Lawns
Frequently asked questions
How much lime can I put on my lawn at once?
For an established lawn, Virginia Cooperative Extension recommends no more than 50 pounds of lime per 1,000 square feet in a single application. If your soil test calls for more, split it into several applications spaced 1 to 6 months apart.
How do I convert tons per acre to pounds per 1,000 square feet?
Multiply tons per acre by 45.9. An acre is 43,560 square feet, so 1 ton (2,000 pounds) per acre equals about 45.9 pounds per 1,000 square feet. To convert pounds per acre, divide by 43.56.
Is pelletized lime better than ground lime?
Both work the same way once they dissolve. Pelletized lime is ground limestone pressed into pellets, so it spreads more evenly with less dust through a lawn spreader. Compare products by the neutralizing value (calcium carbonate equivalent) on the label, not by form.
Should I use dolomitic or calcitic lime?
Dolomitic lime contains magnesium as well as calcium, so it is the better choice when your soil test shows low magnesium. If magnesium is adequate, calcitic lime is fine.
How long does lime take to work?
Lime reacts slowly. It can take several months to a year or more to fully change soil pH, which is why recommendations are spread over time and why it helps to retest the soil every two to three years.