Lime Application Calculator
Enter the area, your current and target soil pH, and the soil type. The calculator returns total lime needed (lb + kg), whether to split into two applications (4 to 6 weeks apart), per-application amount, and the cool-season application window. Dolomitic vs calcitic vs pelletized tradeoffs are summarized in the Pro Tip. If target pH is below current, the tool steers you to sulfur via the testing guide.
Rates use pure calcium carbonate equivalent (the standard residential reference) and assume typical US and Canadian agricultural lime; real performance varies by source, organic matter, and cultivar. Pair with the Soil pH Testing Guide for the testing side, the Fertilizer Calculator for the feeding side, and the Soil Test and Amendment Tracker printable to log every application and pH retest.
Lime needed, split, and timing
Pick the area, enter current and target pH, and pick soil type. Results update live with total lime, number of applications, per-application amount, and the timing window.
Raising loam from 5.5 to 6.5: 50 lb
Total 50 lb (22.7 kg) for 1,000 sq ft (93 m²) at 50 lb per 1,000 sq ft per pH point. Split into 2 applications of 25 lb (11.3 kg) each, 4 to 6 weeks apart, to avoid shocking the soil microbiology. Apply in cool-season fall (Oct to Nov) or early spring (Mar to Apr). Never apply within 2 weeks before or after nitrogen fertilizer.
How to use this calculator
Enter the area in square feet. Enter current soil pH from your most recent test (strip kit, probe meter, or lab). Enter target soil pH per the plant-type table in the Soil pH Testing Guide. Pick soil type: sand, sandy loam, loam, clay loam, or clay. The calculator multiplies (target pH minus current pH) by a soil-specific factor (lb per 1,000 sq ft per pH point) and your area to compute total lime.
Math: lime (lb) = (target pH − current pH) × soil factor × area / 1,000. Soil factors (using pure calcium carbonate equivalent): sand 25, sandy loam 35, loam 50, clay loam 65, clay 80. The calculator triggers split-application guidance any time total lime exceeds 4 lb per 1,000 sq ft.
Tips for success
- Split into two applications when raising pH by 1 point or more. A fast pH swing can shock the soil microbiology, killing beneficial fungi and bacteria the plants depend on. Two doses 4 to 6 weeks apart, applying half each time, gives the soil community time to adjust. The calculator triggers split-application guidance automatically.
- Apply in cool-season fall (Oct to Nov) for the best result. Winter precipitation and freeze-thaw cycles work the lime into the soil before spring growth. Early spring (Mar to Apr) is the backup window. Avoid summer applications: lime sits on the surface and reacts slowly.
- Wait 2 weeks before or after fertilizer applications. Lime can release ammonia from nitrogen fertilizers, wasting both products. Lime first, wait 2 weeks, then fertilize; or fertilize first, wait 2 weeks, then lime.
- Read your soil test for the right lime type. Dolomitic lime contains magnesium and is the right choice for most Northeast US and Eastern Canadian soils (which are typically low in Mg). Calcitic lime is pure calcium; better where Mg is adequate. Pelletized is the easiest to spread but more expensive per pound of active ingredient.
- Re-test 6 to 12 months after application. The soil needs time to react and reach a new equilibrium; testing too early gives a false low reading. Track every application in the Soil Test and Amendment Tracker printable.
Lime types compared
Three lime products dominate residential retail in both US and Canada. Match the type to your soil test and budget.
- Dolomitic lime (Ca + Mg carbonate). Slower-acting; the cooperative-extension default where soil magnesium is low (most of the Northeast US, Eastern Canada including Atlantic provinces, much of Quebec and Ontario). Cost USD 6 to 10 per 40 lb / CAD 9 to 14 per 18 kg at Tractor Supply, Lowe's, Home Depot in the US; Canadian Tire, Home Hardware, Co-op stores in Canada.
- Calcitic lime (high-Cal, pure calcium carbonate). Faster-acting; the right pick where soil magnesium is already adequate (most western and Pacific NW US soils, much of the Canadian Prairies). Cost USD 7 to 12 per 40 lb / CAD 10 to 16 per 18 kg.
- Pelletized lime. Dolomitic or calcitic with a binder; pellets break down into fine particles after moisture exposure. Easier to spread with a residential broadcast spreader (no dust, no clumping), more expensive per pound of active ingredient. Cost USD 12 to 18 per 40 lb / CAD 17 to 25 per 18 kg. Espoma brand widely stocked in both markets.
- Avoid hydrated lime (calcium hydroxide) for residential use. Caustic; raises pH fast but burns plants and shocks soil microbiology. Reserved for industrial applications; not stocked at residential retailers in most markets.
US and Canada timing (3-band model)
The pH scale is universal. Application timing varies by climate band; fall is preferred everywhere because winter weather works the lime into the soil.
- Band 1 (Mild Pacific NW, Southern CA, Mid-US, USDA 7 to 9): October through early November (fall); February through March (spring backup). Mild winters give the longest reaction window.
- Band 2 (Upper US states, Southern Canadian metros Toronto, Vancouver, Halifax; USDA 4 to 6, NRCan 5b to 6b): mid-October through November (fall); April (spring backup). Apply before first hard frost.
- Band 3 (Prairie provinces SK / MB / AB interior, Alaska, Northern Canadian interior; USDA 2 to 4, NRCan 0 to 4): early October before ground freeze (fall); late April once frost retreats and ground is workable (spring backup). Shortest window of the three.
Common mistakes
- Liming without a soil test. Most residential soils need lime; some do not, and some need sulfur (lower pH). A USD 25 / CAD 35 soil test before liming pays back many times over in correct rate and product.
- Single application of a 1-point-or-more raise. Shocks soil microbiology and gives uneven results. Split into two doses 4 to 6 weeks apart.
- Mixing lime with N fertilizer applications. Lime can release ammonia from nitrogen products; wait 2 weeks between applications in either direction.
- Summer application. Lime reacts slowly; granules sit on the surface and lose to runoff and wind. Fall and spring are the windows.
- Using dolomitic where Mg is already adequate. Over-applies magnesium; can lock out calcium uptake. Match lime type to your soil test recommendation, not to the cheapest bag.
- Liming below pH 4.5. Soils that test that acidic need both lime and significant organic matter rebuild; consult a cooperative-extension or provincial agronomy office for a site-specific plan.
- Skipping the post-application retest. Without a 6 to 12 month follow-up test you cannot confirm the change or plan the next amendment. Log every application and retest in the Soil Test and Amendment Tracker printable.
FAQ
How much lime do I need to raise my soil pH by 1 point?
Depends on soil type. Per 1,000 sq ft (about 93 m²) to raise pH by 1.0 point (using pure calcium carbonate equivalent, the standard residential reference): sand 25 lb (11 kg), sandy loam 35 lb (16 kg), loam 50 lb (23 kg), clay loam 65 lb (29 kg), clay 80 lb (36 kg). Clay needs more lime than sand because clay has more cation-exchange sites that buffer pH; literature varies plus or minus 15 percent depending on cultivar, organic matter, and source. Always re-test 6 to 12 months after application to confirm the change.
Why split lime into two applications?
Two reasons. (1) Soil microbiology can be shocked by a fast pH swing; splitting the dose into halves 4 to 6 weeks apart lets the soil community adjust gradually. (2) Practical spreading: an even cover of 50 lb of lime over 1,000 sq ft (4.9 g/m²) is harder to achieve in one pass than two; split applications give a more uniform result. The calculator triggers split-application guidance any time total lime exceeds 4 lb per 1,000 sq ft, which covers most pH-raises of 1 point or more on loam, clay loam, and clay soils.
Dolomitic vs calcitic vs pelletized: which lime should I buy?
Dolomitic lime contains calcium AND magnesium carbonate; slower-acting; ideal where soil magnesium is low (most of the Northeast US and Eastern Canada). Calcitic lime (high-Cal) is pure calcium carbonate; faster-acting; right pick where soil magnesium is adequate. Pelletized lime is dolomitic or calcitic with a binder; easier to spread, more expensive per pound of active ingredient. Prices: dolomitic 6 to 10 USD per 40 lb bag (CAD 9 to 14 per 18 kg bag); calcitic 7 to 12 USD per 40 lb (CAD 10 to 16 per 18 kg); pelletized 12 to 18 USD per 40 lb (CAD 17 to 25 per 18 kg). Read your soil test recommendation before buying; the wrong type wastes the application.
When should I apply lime?
Cool-season fall (October to November) is ideal because winter precipitation and freeze-thaw cycles work the lime into the soil before spring growth. Early spring (March to April) is the backup window before soil dries out. By climate band: Band 1 (Mild Pacific NW, Southern CA, Mid-US) October through early November, or February through March; Band 2 (Upper US, Toronto, Vancouver, Halifax) mid-October through November, or April; Band 3 (Prairies, Northern Canada, Alaska) early October before ground freeze, or late April once frost retreats. Avoid summer applications (slow reaction, granules sit on the surface) and within 2 weeks before or after nitrogen fertilizer (lime can release ammonia from N products).
What if my soil pH is too high?
Lowering soil pH needs sulfur, not lime. Lime always raises pH; sulfur (elemental sulfur or aluminum sulfate) lowers it. If your soil test shows pH above your target, the calculator returns a clear no-lime message and directs you to the Soil pH Testing Guide for sulfur application rates. Common targets: blueberries 4.5 to 5.5 (often needs sulfur on most US and Canadian soils that test at 6.0 or above); potatoes 5.5 to 6.5; rhododendrons + azaleas 4.5 to 6.0. Most yard and garden soils need lime to raise pH; ericaceous beds and acid-loving crops are the main reverse case.