RUSLE Soil Erosion Calculator

Understanding the RUSLE soil erosion calculator — concept and principle

The Revised Universal Soil Loss Equation (RUSLE) estimates long-term average annual soil loss from sheet and rill erosion on a slope. Conservationists, farmers, planners and erosion-control designers use it to compare land uses and practices and to check erosion against a tolerable rate.

Plant cover (C = 0.2) cuts the bare-slope loss of 180 to 36.

How it is calculated

A = R × K × LS × C × P
R: rainfall-runoff erosivity, the erosive energy and intensity of the local rain.
K: soil erodibility, how easily the soil detaches and is carried away.
LS: slope length and steepness factor, equal to 1 for the standard plot (22.1 m long, 9% slope).
C: cover-management factor, from 1 for bare tilled fallow down to near 0 for dense, undisturbed cover.
P: support practice factor, 1 with no practice and lower with contouring, strip-cropping or terracing.

R and K must come from the same unit system. The calculator expects US customary values, as in the defaults, so A is in US tons/acre/yr; it also shows A × 2.2417 in t/ha/yr. SI values convert as R_SI = 17.02 × R_US and K_SI = 0.1317 × K_US.

The principle

The equation was built from thousands of plot-years of US field data. Soil loss on a standard bare plot proved proportional to the rain's erosive energy times its maximum 30-minute intensity (R) and to a soil property (K). Every other condition was expressed as a ratio relative to that standard plot: a longer or steeper slope multiplies the loss (LS), while vegetation and conservation practices reduce it (C and P). Because the factors are multiplied, halving any one of them halves the predicted loss.

Worked example

Inputs: R = 500, K = 0.3, LS = 1.2, C = 0.2, P = 1.
R × K = 500 × 0.3 = 150 (soil loss of the standard bare plot).
× LS: 150 × 1.2 = 180.
× C: 180 × 0.2 = 36; × P: 36 × 1 = 36 US tons/acre/yr.
In metric units: 36 × 2.2417 = 80.7012 t/ha/yr.

Each point is the calculator re-run with only “Rainfall erosivity R (US units)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Rainfall erosivity R (US units)	Soil loss A (US tons/acre/yr)
125	9
250	18
375	27
500	36
625	45
750	54
1,000	72

How to read the result

Compare A with a soil loss tolerance (T value). In the USA, tolerances for cropland are typically 1 to 5 tons/acre/yr, about 2 to 11 t/ha/yr. A result of 36 tons/acre/yr (about 81 t/ha/yr) is far above that and would call for better cover or practices. Since C usually has the widest range, changing cover (mulch, residue, permanent grass) is often the most effective lever.

Common mistakes

Mixing unit systems: SI K values are usually below about 0.1, while K = 0.3 is typical of US customary units.
Expecting the equation to predict a single storm; it gives a long-term annual average.
Applying it to gully, channel or landslide erosion, which it does not cover.

Keep in mind: RUSLE is an empirical planning tool with considerable uncertainty. Erosion and sediment control for construction or regulatory purposes should use locally calibrated factors and follow local requirements and qualified professionals.

Frequently asked questions

What is the difference between USLE and RUSLE?

RUSLE keeps the same six-factor form but updates how R, LS and especially C are computed, including time-varying cover and residue effects.

Sources: W. H. Wischmeier and D. D. Smith, Predicting Rainfall Erosion Losses, USDA Agriculture Handbook No. 537, 1978 · K. G. Renard et al., Predicting Soil Erosion by Water: A Guide to Conservation Planning with RUSLE, USDA Agriculture Handbook No. 703, 1997

Checked 8 Nov 2026. Standard textbook formulas in SI units, computed in your browser. For learning and estimates — real designs must follow your local codes and be checked by a qualified engineer.

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