Soil pH Lime & Sulfur Calculator
Enter your current and target soil pH, your soil type, and the size of your plot to find out exactly how much lime or sulfur to add, split into a safe season-by-season schedule. Nothing uploaded.
Soil pH
Soil texture ?
Application schedule
Space applications roughly 3-4 months apart (for example, fall and spring) so the change happens gradually and roots aren't shocked.
Soil pH buffering and amendment timing
Why soil texture affects amendment rates
Soil texture determines how much "buffering" (resistance to pH change) you face. Sandy soil has large pores and little clay, so it changes pH quickly with small amounts of lime or sulfur - about 4 lbs of lime per 100 square feet to raise pH by 1.0 unit. Loam (a balanced mix of sand, silt, and clay) needs 7.5 lbs per 100 square feet. Clay-heavy soil resists pH change because clay particles bind hydrogen ions - you need 11 lbs of lime per 100 square feet to budge pH by 1.0 unit. For example, to raise a sandy 500-square-foot bed from 5.5 to 6.5 pH takes 20 lbs of lime, but the same change in clay soil takes 55 lbs. A soil test (available from your extension service) tells you your exact texture.
Why amendments are split across seasons
Applying all the lime or sulfur at once risks overshooting your target and shocking plant roots. Instead, the calculator splits large amendments into 2-4 applications spread 3-4 months apart (typically fall and spring). This lets the amendment work gradually, settle into the soil, and stabilize before the next application. Between applications, water and soil microbes work to dissolve and distribute the amendment. This staged approach also gives you a safety check - you can test pH after the first application and adjust future amounts if needed.
FAQ
Should I use agricultural lime or dolomitic lime?
Agricultural lime (calcium carbonate) raises pH and adds calcium. Dolomitic lime also adds magnesium. Use dolomitic lime if your soil test shows low magnesium, otherwise agricultural lime is fine and often cheaper. Do not confuse either with hydrated lime (calcium hydroxide), which acts too fast and is harder to control.
How long does lime take to work?
Lime reacts slowly with soil. Most of the pH shift happens within 2-3 months, but full stabilization takes 6-12 months. Elemental sulfur takes even longer - 3-6 months for noticeable change, a year for completion. This is why amendments should be applied in advance of planting if possible, or at least early in the season.
What if I apply too much and overshoot?
Overshooting lime (raising pH too high) is hard to fix quickly - you can add sulfur, but it takes months. Overshooting sulfur (making soil too acidic) is easier to reverse with lime. Always start with a half-application and test after 6 weeks. A soil pH meter costs 15-40 dollars and gives you feedback to avoid guessing.