Estimate annual soil loss using the Universal Soil Loss Equation (USLE). Enter R, K, LS, C, and P factors for erosion prediction.
The Soil Erosion Calculator uses the Universal Soil Loss Equation (USLE) to predict average annual soil loss from sheet and rill erosion on agricultural fields. Developed by Wischmeier and Smith in 1978, the USLE multiplies five factors: rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover management (C), and support practices (P).
The USLE predicts long-term average soil loss — not individual storm events. It is widely used by USDA NRCS for conservation planning, nutrient management plans, and compliance with the Soil Conservation Act. Predicted soil loss is compared against the tolerable soil loss rate (T value), typically 3–5 tons/ac/year for most soils.
While more advanced models (RUSLE2, WEPP) have superseded USLE for some applications, the original equation remains a valuable tool for quick field estimates and understanding the relative importance of each erosion control factor. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation.
Erosion is the single greatest long-term threat to soil productivity. The USLE helps you quantify current erosion rates and evaluate the effectiveness of conservation practices (cover crops, contour farming, no-till) before investing in them. Having a precise figure at your fingertips empowers better planning and more confident decisions. Manual calculations are error-prone and time-consuming; this tool delivers verified results in seconds so you can focus on strategy.
A = R × K × LS × C × P Where: A = Predicted annual soil loss (tons/ac/yr) R = Rainfall-runoff erosivity factor K = Soil erodibility factor (ton·ac·hr / hundreds of ft-tonf·ac·in) LS = Slope length and steepness factor (dimensionless) C = Cover management factor (0–1, lower is better) P = Support practice factor (0–1, lower is better)
Result: 10.8 tons/ac/yr
A = 150 × 0.30 × 1.5 × 0.20 × 0.80 = 10.8 tons/ac/yr. This exceeds the typical T value of 5 tons/ac/yr. Switching to no-till (C=0.05) would reduce loss to 2.7 tons/ac/yr — below T value.
If predicted soil loss exceeds the T value, conservation practices must be improved. The most effective options are: reducing tillage (lower C), adding cover crops (lower C), contour farming (lower P), and terracing (lower P and effectively shorter slope length). Each factor is independent, so you can model "what-if" scenarios by changing one factor at a time.
USLE is empirical, not process-based. It doesn’t predict event-by-event erosion, sediment delivery to waterways, or deposition. It assumes uniform slopes and uniform management. For complex landscapes, use RUSLE2 or WEPP. Despite limitations, USLE remains useful for rapid comparative analysis.
Eroded soil carries away organic carbon — the most fertile component of the topsoil. Each ton of eroded soil may contain 20–40 lbs of organic carbon plus associated nutrients. Erosion control is therefore also a carbon conservation strategy that maintains long-term soil productivity.
NRCS publishes R factor maps for the entire U.S. in Agriculture Handbook 703. Your local NRCS office can provide the value for your county. Online tools like the RUSLE2 database also provide R values.
There is no "good" K — it’s an inherent property of your soil. Sandy soils have low K (0.02–0.15), clay soils moderate K (0.15–0.30), and silt loams have high K (0.40–0.65). You manage around K by adjusting C and P factors.
LS combines slope length and steepness. For a 200-foot slope at 4% grade, LS ≈ 0.7. For a 400-foot slope at 8%, LS ≈ 2.5. NRCS provides LS factor tables, or use: LS = (λ/72.6)^m × (65.41 sin²θ + 4.56 sinθ + 0.065).
Continuous clean-tilled fallow: 1.0. Conventional till corn: 0.30–0.50. No-till corn: 0.03–0.08. Pasture/hay: 0.003–0.01. The C factor is the most manageable variable in the equation.
The T value was established as the maximum erosion rate that maintains long-term productivity. However, it takes 300–1,000 years to form 1 inch of topsoil, and 5 tons/ac removes about 1/30 inch per year. Many soil scientists argue that T should be lower.
No. USLE only predicts sheet and rill erosion from water. Gully erosion requires separate assessment. Wind erosion uses the Wind Erosion Equation (WEQ) or WEPS model. For a complete erosion assessment, all types should be evaluated.