Behind the calculation
What CivilSolve checks
The calculators compute the numbers and show their steps. When you submit a word problem, AI reads the inputs and writes an explanation. Here is how those parts are checked, and where you still need to review the result.
Calculators and submitted problems
Direct calculators run without AI. You enter the values yourself and receive the worked calculation. For a submitted word problem, AI helps read the inputs and explain the result through the steps below.
Read the problem
AI matches your text and optional figure to a supported calculator and fills in its inputs. The selected calculator and extracted values are shown so you can compare them with your question. This interpretation can be wrong.
Calculate
Engineering code checks the input format and units, then computes the result. It records the assumptions, equations, substitutions and answers. The same inputs produce the same calculation.
Explain the result
AI writes an explanation from the calculator’s output, without seeing your original submission. The worked calculation remains visible alongside this explanation.
Check the explanation’s numbers
An automated audit looks for numbers in the explanation that do not appear in the calculation. If it finds a mismatch, the explanation is generated once more. A repeated mismatch is flagged. This checks the numbers, not every claim in the prose.
How the calculators are tested
Each calculator has reference problems with expected answers from published sources or independent hand calculations. Each record identifies its source and verification method. These cases are part of the automated test suite; they check specific examples rather than proving every possible use is correct.
- Reference answers are never fabricated.
- Reference answers are never generated by an AI.
- A solver is never used to check itself — answers come from published sources or independent hand computation, recorded in the test file.
An example from the test suite
- problem
- US single catchment: C=0.3, i=2 in/hr, A=5 ac
- source
- Rational formula (NCEES FE Reference Handbook); exact unit conversion — Q = C·i·A with ac·in/hr → cfs carrying the 1.00833 factor
- verified by
- hand-recomputed
- derivation
- i = 2·0.0254/3600 = 1.41111e-5 m/s; A = 20234.282 m²; Q = 0.3·1.41111e-5·20234.282 = 0.0856583 m³/s = 3.025 cfs (folklore shortcut gives 3.0).
- must produce
- peakFlow = 3.025 cfscompositeC = 0.3
Inside this release
These counts come from this release’s calculator registry and reference cases.
54
calculators
212
reference problems with checked answers
58
test cases for invalid inputs
9
disciplines covered
Units and conventions
- All solvers compute in SI internally; your units are converted and dimension-checked at the boundary, and answers display in SI or US customary — your choice.
- “lb” is read as pound-force in load contexts (the civil convention), and the solution says so whenever that reading was applied.
- Numbers are rounded only for display, with significant figures stated. The computation itself is full-precision floating point.
- Iterative solutions (normal depth, friction factors, rates of return) report their convergence, and warn when a result sits near a sensitive edge.
Before you rely on a result
A calculation can use the wrong setup
AI can misread a diagram, extract the wrong value or choose an unsuitable calculator. Review the named method, inputs, units and assumptions. Passing the numeric audit does not establish that the original problem was understood correctly.
Coverage is limited
Each calculator supports specific problem types. Recognized missing data, unsupported topics and invalid inputs produce a message instead of a result. These checks cannot catch every possible modeling error. CivilSolve also does not mark or diagnose your handwritten solution.
Your course may use a different convention
Solvers that touch design standards (sight distance, soil classification) name the standard they implement. Your course may use a different edition — check the cited convention on the solution.
Use it as a study tool
CivilSolve is a study tool. It is not a substitute for engineering judgment, review, or a licensed engineer's seal.
Who makes this
CivilSolve is a Runestone Labs product. Our aim is to make the calculation easy to inspect, with its inputs, method and limitations visible.