Zerdly

Logging Interval Totals Calculator

Adds up your logged sub-interval lengths and checks that they sum to the drilled run length, flagging gaps or overlaps before you save the log. It is a fast quality check for core loggers and data validators.

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How to use this calculator

Enter Values

Enter your values and press Calculate to see results.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter each logged sub-interval length in metres — up to five — leaving unused rows blank.
  2. Enter the expected (drilled) run length for that stretch of hole.
  3. Read the total, the signed difference against expected, and whether it balances.

How it works

The tool sums the sub-interval lengths you enter and subtracts the expected run length: difference = sum − expected. A positive difference means you have logged more than was drilled (likely an overlap or duplicated interval); a negative difference means a gap or missing interval.

It reports 'OK' when the absolute difference is under 0.005 m (a 5 mm rounding tolerance) and 'check logging' otherwise. This catches the classic logging errors — a FROM/TO typo, a skipped interval, or two intervals that overlap — before the log is committed.

Worked example

A 2.00 m run in four pieces. Sub-intervals of 0.50, 0.75, 0.60 and 0.15 m sum to 2.00 m. Against an expected run length of 2.00 m the difference is 0.000 m, so it balances (OK). If the last piece had been mistyped as 0.05 m, the sum would be 1.90 m, a difference of −0.10 m → 'check logging'.

Common mistakes

  • Entering an overlapping interval, which makes the sum exceed the run length (a positive difference).
  • Missing a sub-interval entirely, which shows up as a negative difference (a gap).
  • Reading the difference sign the wrong way — positive is over-logged, negative is short.

Frequently asked questions

What does 'balances' mean here?

That the logged sub-intervals add up to the drilled run length within a 5 mm tolerance, so there are no gaps or overlaps.

Why is there a 5 mm tolerance?

Depths are usually logged to the centimetre, so tiny rounding differences are harmless. Anything larger than 5 mm points to a real logging error.

What does a positive difference mean?

Your sub-intervals sum to more than the run length — usually an overlap or a duplicated interval.

What does a negative difference mean?

Your sub-intervals sum to less than the run length — usually a gap or a missing interval.

How many sub-intervals can I check?

Up to five per run. For a longer run, reconcile it in blocks that share a common expected length.

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Tip: Enter any known values to calculate the remaining results.

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