Cumulative Movement Calculator
Add up successive survey increments to get the total accumulated slope movement since the baseline reading. Used by geotechnical and monitoring teams to track how far a prism, extensometer or survey point has moved overall, and its average rate.
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How to use this calculator
- Enter each survey increment (the movement between successive readings) in millimetres — up to six, and they can be negative.
- Leave unused increment boxes blank; the tool sums only the ones you fill in.
- Optionally enter the total elapsed time in days to also get the average movement rate.
How it works
Cumulative movement is the algebraic sum of the successive increments: Σinc. Each increment is the change between two readings, so summing from the baseline reproduces the net displacement to date. Because increments are signed, a recovery (negative increment) correctly reduces the running total. The result is also shown in metres.
If you provide the total elapsed time, the tool divides the cumulative movement by that time to give the average rate over the whole record — a long-run velocity to sit alongside the latest interval rate.
Worked example
Four increments totalling 5.5 mm. Increments of +2, −1, +3 and +1.5 mm sum to 5.5 mm cumulative movement (0.0055 m) across four readings. If those readings span 10 days, the average rate is 5.5 / 10 = 0.55 mm/day.
Common mistakes
- Dropping the minus sign on a recovery increment, which overstates the cumulative total.
- Entering cumulative totals instead of increments — this tool wants the change between readings.
- Using inconsistent units; every increment must be in millimetres.
Frequently asked questions
What is cumulative slope movement?
The total distance a monitored point has moved since the baseline survey, found by adding all the between-reading increments. It is the value normally plotted on a movement-vs-time chart.
Should increments be positive or negative?
Use your survey's sign convention: positive for movement in the monitored direction, negative for recovery. The calculator adds them algebraically so reversals reduce the total.
How is the average rate different from the latest rate?
The average rate is cumulative movement ÷ total elapsed time — a smoothed long-run figure. The latest interval rate reflects only the most recent reading and reacts faster.
Why convert to metres?
Large or long-running slope records are often plotted in metres. The tool shows both mm and m so the number fits whichever axis your plot uses.
Related tools
- Prism Movement Rate Calculator
- Rolling Average Movement Calculator
- Prism Movement TARP Checker
- Crack Displacement Calculator
- Radar Prism Displacement Comparison Tool
- Piezometer Trend Calculator
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Tip: Enter any known values to calculate the remaining results.
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