The envelope from the soil lab lands on the counter, you open it, and there it is: a pH that says the soil is acidic, plus a column of numbers that might as well be in another language. The pH is the easy part. The number that decides how much lime to buy is hiding in that other column, and most guides skip straight past it.
This calculator does the part the guides skip. It turns the numbers on your own soil-test report into pounds of lime or sulfur for your lawn, and it tells you how to split the job so you don’t burn the grass doing it all at once. The tables it reads from are printed further down the page, so you can look your number up by hand, too.
The soil pH calculator
Pick a direction first — raising pH with lime, or lowering it with sulfur — then fill in the numbers from your soil-test report. Lime needs the buffer number from the report; sulfur needs the fizz check below. If you don’t have a soil test yet, start with our guide to testing your lawn soil at home — only a lab report carries the buffer number lime needs.
From your soil-test report — the pH reading, not the buffer number.
Most lawn grasses grow best near 6.5. The table further down lists the best range for each grass.
Required — this is the number that sets your lime rate. On a Penn State report it is printed as “Acidity” at the bottom; other labs call it buffer acidity or exchangeable acidity. If your report doesn’t have one, leave it blank and the calculator will tell you to get a soil test instead of guessing.
CCE is a strength rating: how strong your bag of lime is next to pure limestone, which rates 100. It is printed on the bag label — leave it at 100 if you’re not sure.
Fizz means the soil holds carbonates, and carbonates fight sulfur — the calculator will say so instead of giving you a number.
Blueberries and rhododendrons want the low end; most lawns want 6.5. The table further down lists the best range for each grass.
Squeeze a moist handful: sand falls apart, loam holds a short ribbon, clay holds a long one.
What the number means
Three numbers come back. The rate is pounds per 1,000 square feet, the total is the rate times your area — the number you actually shop with — and the plan splits the total into applications that stay under the safe single dose, with months between them.
The calculator looks up your buffer number in the lime table, turns pounds per acre into pounds per 1,000 square feet, and adjusts for how strong your bag of lime is. For sulfur it reads your pH and soil type straight off the table and does the same area math. For lime it also names the table row it used, so you can check it against the big table below.
CCE is just a strength rating — how strong your bag of lime is next to pure limestone, which rates 100. A bag rated 90 needs a little more product to do the same job, and the calculator makes that adjustment for you instead of folding it in silently.
If you don’t have a buffer number, the calculator won’t guess. It will tell you to get a soil test, because pH alone can’t set a lime rate — explained below.
How to put lime down
On an established lawn, never put down more than 100 pounds of lime per 1,000 square feet in a single application. If your total runs higher, split it into two or more passes, three to six months apart, and water each one in. A new lawn is different: work the full amount into the top six inches before you seed, where it can start working right away.
Lime works slowly from the surface — on an established lawn, expect the full change to take a season or more. Aerating first helps on a compacted lawn, since it opens the way down. Test again before you add more, and follow the rest of your soil-test report for fertilizer — our fertilizer calculator turns the bag’s numbers into pounds per 1,000 square feet. If your lab recommended dolomitic lime, use it: it also adds magnesium, which calcitic lime doesn’t.
One more thing the bag won’t tell you: hydrated lime and quicklime act faster but can burn grass, so they belong on bare soil before a lawn goes in, not on a lawn you already have. Gypsum, for all its reputation, doesn’t change pH at all.
Why pH alone can’t set a lime rate
Soil pH measures the acid floating in the soil water right now. Buffer acidity — the stored acidity, held on the soil particles — is the part the pH reading can’t see, and it’s the part that decides how much lime it takes to move the number. Two lawns can test at the same pH and still need very different amounts of lime, because one soil holds far more stored acidity than the other.
That’s why the buffer number lives on the lab report and not on a hardware-store kit. On a Penn State report it is printed as “Acidity” at the bottom; other labs call it buffer acidity or exchangeable acidity. If your report gives you a buffer pH instead — the SMP or Sikora test, common in the Midwest — use your lab’s own recommendation and check it against the Iowa table below, because the two tests speak different numbers.
If you haven’t tested at all, start with a lab test — our look at the best soil test kits for lawns sorts out which kits are worth buying.
Lowering pH with sulfur
Sulfur lowers pH the slow way: soil bacteria turn it into acid over months, so expect the change in three to six months and test again in four to six months before you add more. Never put down more than 15 pounds per 1,000 square feet at once — if your total runs higher, split it and wait for the retest between rounds.
Do the fizz check first. A few drops of vinegar on a clod of soil: if it bubbles, the soil holds carbonates, and carbonates will fight the sulfur every step of the way. For acid-loving plants in that kind of soil, a raised bed or container filled with fresh mix is the reliable route — and pine needle mulch helps keep a blueberry bed acidic once it’s planted.
The calculator also shows an aluminum sulfate equivalent — six times the sulfur figure — as a rough equivalent for the same job, not a second recommendation.
What this calculator doesn’t tell you
This tells you how much lime or sulfur to put down for the area you measured — not how often to feed the lawn, what your soil needs for nutrients, or how your weather and drainage will treat the application.
Bottom line
Get the test, use the buffer number on it, and put the amendment down in splits. That is the whole job — everything else on this page is just the tables to check your work against.
Worked examples
Six examples, worked all the way through, so you can check the calculator against them. The arithmetic, in plain words: take the pounds per acre from the table and divide by 43.56 to get pounds per 1,000 square feet; multiply by your area in thousands of square feet for the total; and divide the rate by the single-dose limit, rounding up, for the number of applications.
Lime, buffer acidity 3.9, target pH 6.5, 5,000 square feet. The table row for acidity 3.9 gives 3,000 pounds of lime per acre at a 6.5 goal. Divide by 43.56 and that’s 68.9 pounds per 1,000 square feet — times five for the area, 344 pounds in total. One application, since 68.9 sits under the 100-pound single-dose limit.
Lime, buffer acidity 6.5, target pH 6.5, 5,000 square feet. The row for acidity 6.5 gives 5,000 pounds per acre, which works out to 114.8 pounds per 1,000 square feet and 574 pounds for the area. That’s over the single-dose limit, so it goes down as two applications of 57.4 pounds per 1,000 square feet, three to six months apart. A soil that needs this much lime from its buffer reading can sit well above what a texture-only estimate would guess — that is why the lab number governs.
The same lawn, but the bag is rated 90% CCE. Divide 114.8 by 0.90 and the rate becomes 127.5 pounds per 1,000 square feet — 638 pounds for 5,000 square feet, still two applications. Penn State’s own example works the same way: a recommendation of 5 pounds per 100 square feet with a product rated 70% CCE needs 7 pounds per 100 square feet.
Sulfur, loam soil, pH 7.5 down to 6.5, 5,000 square feet. The table gives 20 pounds of sulfur per 1,000 square feet — 100 pounds in total. The single-dose limit is 15, so it goes down as two applications of 10 pounds per 1,000 square feet, with a retest in four to six months before any more. The aluminum sulfate equivalent is 120 pounds per 1,000 square feet.
Lime for a lab that reports an SMP buffer pH instead of a Mehlich acidity. A buffer pH of 6.5, six inches deep, target pH 6.5, gives 2,800 pounds per acre from the Iowa table — 64.3 pounds per 1,000 square feet, or 321 pounds for 5,000 square feet. This is a different test with different numbers, so don’t mix it with the calculator above; use your lab’s own recommendation.
A different way to reach a sulfur number, for soils where the lab reports CEC and base saturation. CEC is a measure of how much nutrition the soil can hold; base saturation is how much of that holding space is already filled with calcium, magnesium, and potassium. With a CEC of 5.7 and base saturation falling from 97% to 60%, the equation gives 5.7 × 0.37 × 320 = 675 pounds per acre, or 15.5 pounds per 1,000 square feet. That example comes from North Carolina State’s guide, for a soil moving from pH 7.1 to 5.0 — useful if your lab reports CEC and base saturation and no sulfur table.
Reference tables
Every table the calculator uses, printed in full. Look your number up by hand here if you like — the calculator reads from these same tables.
Lime by buffer acidity (Penn State)
Pounds of lime per acre, by the acidity on your soil-test report and the pH you’re aiming for. If your pH is already at or above your target, no lime is needed.
| Buffer acidity (meq/100 g) | pH goal 7.0 | pH goal 6.5 | pH goal 6.0 | pH goal 5.5 | pH goal 5.0 |
|---|---|---|---|---|---|
| 2.0 | 2,000 | 2,000 | 2,000 | 2,000 | 2,000 |
| 2.6 | 3,000 | 2,000 | 2,000 | 2,000 | 2,000 |
| 3.3 | 3,000 | 2,000 | 2,000 | 2,000 | 2,000 |
| 3.9 | 4,000 | 3,000 | 2,000 | 2,000 | 2,000 |
| 4.6 | 5,000 | 3,000 | 2,000 | 2,000 | 2,000 |
| 5.2 | 5,000 | 4,000 | 2,000 | 2,000 | 2,000 |
| 5.8 | 6,000 | 4,000 | 2,000 | 2,000 | 2,000 |
| 6.5 | 7,000 | 5,000 | 3,000 | 2,000 | 2,000 |
| 7.1 | 7,000 | 5,000 | 4,000 | 2,000 | 2,000 |
| 7.8 | 8,000 | 6,000 | 4,000 | 2,000 | 2,000 |
| 8.4 | 8,000 | 6,000 | 5,000 | 3,000 | 2,000 |
| 9.0 | 9,000 | 7,000 | 5,000 | 3,000 | 3,000 |
| 9.7 | 10,000 | 8,000 | 6,000 | 4,000 | 3,000 |
| 10.3 | 10,000 | 8,000 | 6,000 | 4,000 | 3,000 |
| 11.0 | 11,000 | 9,000 | 7,000 | 4,000 | 3,000 |
| 11.6 | 12,000 | 9,000 | 7,000 | 5,000 | 4,000 |
| 12.3 | 12,000 | 10,000 | 8,000 | 5,000 | 4,000 |
| 12.9 | 13,000 | 11,000 | 8,000 | 6,000 | 4,000 |
| 13.5 | 14,000 | 11,000 | 9,000 | 6,000 | 5,000 |
| 14.2 | 14,000 | 12,000 | 9,000 | 6,000 | 5,000 |
| 14.8 | 15,000 | 12,000 | 10,000 | 7,000 | 6,000 |
| 15.5 | 16,000 | 13,000 | 10,000 | 7,000 | 6,000 |
| 16.1 | 16,000 | 14,000 | 11,000 | 8,000 | 6,000 |
| 16.8 | 17,000 | 14,000 | 11,000 | 8,000 | 6,000 |
| 17.4 | 17,000 | 15,000 | 12,000 | 8,000 | 7,000 |
| 18.0 | 18,000 | 15,000 | 12,000 | 9,000 | 7,000 |
| 18.7 | 19,000 | 16,000 | 13,000 | 9,000 | 7,000 |
| 19.3 | 19,000 | 17,000 | 13,000 | 10,000 | 8,000 |
| 20.0 | 20,000 | 17,000 | 14,000 | 10,000 | 8,000 |
| 20.6 | 21,000 | 18,000 | 14,000 | 10,000 | 8,000 |
| 21.2 | 21,000 | 18,000 | 15,000 | 11,000 | 9,000 |
| 21.9 | 22,000 | 20,000 | 15,000 | 11,000 | 9,000 |
| 22.5 | 23,000 | 20,000 | 16,000 | 12,000 | 9,000 |
| 23.2 | 23,000 | 20,000 | 16,000 | 12,000 | 10,000 |
| 23.8 | 24,000 | 21,000 | 17,000 | 12,000 | 10,000 |
| 24.5 | 25,000 | 21,000 | 17,000 | 13,000 | 10,000 |
| 25.1 | 25,000 | 22,000 | 18,000 | 13,000 | 11,000 |
| 25.7 | 26,000 | 23,000 | 18,000 | 14,000 | 11,000 |
Sulfur by pH and soil type (UMass)
Pounds of elemental sulfur (plain sulfur) per 1,000 square feet. Find your current pH, then the target pH, and read the rate for your soil type.
| Current pH | Target pH | Sand | Loam | Clay |
|---|---|---|---|---|
| 4.0 | 4.0 | 0 | 0 | 0 |
| 4.5 | 4.0 | 4 | 10 | 16 |
| 4.5 | 4.5 | 0 | 0 | 0 |
| 5.0 | 4.0 | 8 | 20 | 32 |
| 5.0 | 4.5 | 4 | 10 | 16 |
| 5.0 | 5.0 | 0 | 0 | 0 |
| 5.5 | 4.0 | 12 | 29 | 47 |
| 5.5 | 4.5 | 8 | 20 | 32 |
| 5.5 | 5.0 | 4 | 10 | 16 |
| 5.5 | 5.5 | 0 | 0 | 0 |
| 6.0 | 4.0 | 15 | 38 | 61 |
| 6.0 | 4.5 | 12 | 29 | 47 |
| 6.0 | 5.0 | 8 | 20 | 32 |
| 6.0 | 5.5 | 4 | 10 | 16 |
| 6.0 | 6.0 | 0 | 0 | 0 |
| 6.5 | 4.0 | 19 | 48 | 77 |
| 6.5 | 4.5 | 15 | 38 | 61 |
| 6.5 | 5.0 | 12 | 29 | 47 |
| 6.5 | 5.5 | 8 | 20 | 32 |
| 6.5 | 6.0 | 4 | 10 | 16 |
| 6.5 | 6.5 | 0 | 0 | 0 |
| 7.0 | 4.0 | 23 | 57 | 92 |
| 7.0 | 4.5 | 19 | 48 | 77 |
| 7.0 | 5.0 | 15 | 38 | 61 |
| 7.0 | 5.5 | 12 | 29 | 47 |
| 7.0 | 6.0 | 8 | 20 | 32 |
| 7.0 | 6.5 | 4 | 10 | 16 |
| 7.0 | 7.0 | 0 | 0 | 0 |
| 7.5 | 4.0 | 27 | 67 | 107 |
| 7.5 | 4.5 | 23 | 57 | 92 |
| 7.5 | 5.0 | 19 | 48 | 77 |
| 7.5 | 5.5 | 15 | 38 | 61 |
| 7.5 | 6.0 | 12 | 29 | 47 |
| 7.5 | 6.5 | 8 | 20 | 32 |
| 7.5 | 7.0 | 4 | 10 | 16 |
| 8.0 | 4.0 | 30 | 76 | 123 |
| 8.0 | 4.5 | 27 | 67 | 107 |
| 8.0 | 5.0 | 23 | 57 | 92 |
| 8.0 | 5.5 | 19 | 48 | 77 |
| 8.0 | 6.0 | 15 | 38 | 61 |
| 8.0 | 6.5 | 12 | 29 | 47 |
| 8.0 | 7.0 | 8 | 20 | 32 |
Lime estimates by texture (Kentucky)
An estimate only, for a six-inch root zone raised to pH 6.5 before planting. Your lab’s buffer-based number overrides it.
| Soil texture | From pH 4.5 (lb/1,000 sq ft) | From pH 5.5 (lb/1,000 sq ft) |
|---|---|---|
| Sand and loamy sand | 30–50 | 20–30 |
| Loam | 80–130 | 45–75 |
| Clay loam and clay | 150–190 | 90–100 |
Best pH by grass (Kentucky)
| Grass | Best pH range |
|---|---|
| Bermudagrass | 6.0–7.0 |
| Chewings fescue | 5.5–6.5 |
| Creeping red fescue | 5.5–6.5 |
| Hard fescue | 5.0–6.5 |
| Kentucky bluegrass | 6.0–7.0 |
| Meadow fescue | 5.0–7.0 |
| Perennial ryegrass | 6.0–7.0 |
| Tall fescue | 5.5–6.5 |
| Zoysiagrass | 6.0–7.0 |
Lime and sulfur by texture (Michigan State)
Lime, in pounds of ground limestone per 100 square feet, to raise pH to 6.5. Sulfur, in pounds per 100 square feet, to lower pH to 6.0.
| Current pH | Sandy loam | Loam | Clay loam |
|---|---|---|---|
| 5.0 | 8 | 10 | 15 |
| 5.5 | 6 | 8 | 10 |
| 6.0 | 3 | 4 | 6 |
| Current pH | Sandy loam | Loam | Clay loam |
|---|---|---|---|
| 7.5 | 1.8 | 2.5 | 3.9 |
| 7.0 | 1.4 | 2.0 | 3.1 |
| 6.5 | 0.8 | 1.2 | 1.9 |
Sulfur and lime (Ohio State)
Sulfur, in pounds of 95% pure sulfur per 1,000 square feet, to bring a six-inch layer of soil to pH 6.5. Lime, in pounds per 1,000 square feet, for a seven-inch layer.
| From pH | Sand | Loam | Clay |
|---|---|---|---|
| 7.0 | 2.3 | 3.4 | 6.9 |
| 7.5 | 11.5 | 18.4 | 23.0 |
| 8.0 | 27.5 | 34.4 | 45.9 |
| 8.5 | 45.9 | 57.4 | 68.8 |
| Soil | pH 4.5 to 5.5 | pH 5.5 to 6.5 |
|---|---|---|
| Sand, loamy soil | 23 | 28 |
| Sandy loam | 37 | 60 |
| Loam | 55 | 78 |
| Silt loam | 69 | 92 |
| Clay loam | 87 | 106 |
| Muck | 174 | 197 |
Sulfur for home gardens (Penn State)
Pounds of sulfur per 100 square feet, for a loam soil. Heavier soils (silt loams) need a third more than the table shows; lighter soils (sandy loams) need half. If 4 or more pounds per 100 square feet are needed, split the amount in half and apply the halves six months apart. For lime, if 11 to 20 pounds per 100 square feet are recommended, split it in two, six months apart; if 21 or more, split it in three, six months apart.
| From current pH | To 7.5 | To 7.0 | To 6.5 | To 6.0 | To 5.5 |
|---|---|---|---|---|---|
| 8.0 | 0.50 | 1.00 | 2.00 | 3.00 | 4.00 |
| 7.5 | — | 0.75 | 1.25 | 2.50 | 3.50 |
| 7.0 | — | — | 0.75 | 1.25 | 2.50 |
| 6.5 | — | — | — | 1.00 | 1.75 |
| 6.0 | — | — | — | — | 1.50 |
Sulfur for loamy soils (Clemson)
Pounds of sulfur per 10 square feet, for loamy soils. Reduce by a third for sandy soils, increase by half for clay soils.
| Present pH | To 6.5 | To 6.0 | To 5.5 | To 5.0 | To 4.5 |
|---|---|---|---|---|---|
| 8.0 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 |
| 7.5 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 |
| 7.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 |
| 6.5 | — | 0.1 | 0.2 | 0.3 | 0.4 |
| 6.0 | — | — | 0.1 | 0.2 | 0.3 |
Lime by buffer pH (Iowa State)
Pounds of lime per acre for a six-inch depth, from the SMP buffer test. This is a different test from the Mehlich acidity the calculator uses — a buffer pH of 6.5 is not an acidity of 6.5.
| Buffer pH | To pH 6.5 | To pH 6.9 |
|---|---|---|
| 7.0 | 0 | 1,100 |
| 6.9 | 0 | 1,900 |
| 6.8 | 600 | 2,700 |
| 6.7 | 1,300 | 3,500 |
| 6.6 | 2,100 | 4,400 |
| 6.5 | 2,800 | 5,200 |
| 6.4 | 3,500 | 6,000 |
| 6.3 | 4,200 | 6,800 |
| 6.2 | 5,000 | 7,700 |
| 6.1 | 5,700 | 8,500 |
| 6.0 | 6,400 | 9,300 |
| 5.9 | 7,100 | 10,100 |
| 5.8 | 7,900 | 11,000 |
| 5.7 | 8,600 | 11,800 |
Sources
- Penn State Agricultural Analytical Services Lab, “Lime Recommendations” — agsci.psu.edu/aasl/soil-testing/fertility/handbooks/agronomic/tables/lime-recommendations — fetched in full Nov 10, 2026; re-checked Nov 11, 2026.
- Penn State Agricultural Analytical Services Lab, “Home Garden” report notes (sulfur table, CCE formula, split rules) — agsci.psu.edu/aasl/online-report/home-garden — fetched in full Nov 10, 2026.
- University of Kentucky, AGR-214, “Liming Kentucky Lawns” (Munshaw & Ritchey) — publications.mgcafe.uky.edu/files/AGR214.pdf — fetched in full Nov 10, 2026.
- UMass Soil and Plant Nutrient Testing Laboratory, “Adjusting Soil pH” (SPTTL_3, January 2015, Tracy Allen) — umass.edu/agriculture-food-environment/sites/ag.umass.edu/files/fact-sheets/pdf/spttl_3_adjusting_soil_ph_0.pdf — fetched in full Nov 10, 2026; re-checked Nov 11, 2026.
- Michigan State University Extension, “Making the most out of your soil test” (Finneran & Wilson, published May 2012, updated March 2018) — homesoiltest.msu.edu/sites/default/files/pdf/soil_ph.pdf — fetched in full Nov 10, 2026.
- Ohio State University Extension (Gary Gao), “Knowing Your Nitrogen” — stormwater.com/erosion-control/vegetation-management/article/13003103/knowing-your-nitrogen — fetched in full Nov 10, 2026.
- Clemson Cooperative Extension, HGIC 1650, “Changing the pH of Your Soil” (originally published 06/99) — hgic.clemson.edu/factsheet/changing-the-ph-of-your-soil — fetched in full Nov 10, 2026.
- Iowa State University Extension, PM 1688, “A General Guide for Crop Nutrient and Limestone Recommendations in Iowa” (revised November 2002), Table 14 — agronext.iastate.edu/soilfertility/info/PM 1688 2002.pdf — fetched in full Nov 10, 2026.
- NC State Extension, AG-439-88, “Calculating the Rate of Acidifiers to Lower the pH of North Carolina Soils” (published July 23, 2020; reviewed/revised June 25, 2025) — content.ces.ncsu.edu/calculating-the-rate-of-acidifiers-to-lower-the-ph-of-north-carolina-soils — fetched in full Nov 10, 2026.
- Penn State Agricultural Analytical Services Lab, “Home Lawn to Maintain” crop sheet (code 2001, revised Dec 28, 2017) — agsci.psu.edu/aasl/soil-testing/fertility/handbooks/turf/recommendations/2001-home-lawn-maintain — fetched in full Nov 11, 2026.
- Iowa State University Extension, PM 1688 (revised February 2023), Table 16 — soilhealthnexus.org/wp-content/uploads/sites/455/2025/10/PM1688.pdf — checked Nov 11, 2026; values identical to the 2002 Table 14.
