Excavation Time Calculator

How the excavation time calculator works

Digging time on a small job comes down to one number: how long the machine takes to move each cubic metre of ground. This calculator multiplies the volume to be dug by that rate to get machine-hours, divides the hours by your productive working day to get days on site, and multiplies the hours by your machine-and-operator rate to get a cost. It suits a mini-digger or backhoe job such as a footing trench, a patio or driveway dig-out, a pond or a small basement lower, and it works for hand digging too if you enter a hand-dig rate.

The rate is always in hours per cubic metre, even on the US side, and the calculator converts cubic yards to cubic metres before it multiplies. So the US default of 26 yd³ becomes 26 × 0.7646 = 19.88 m³, and 19.88 × 0.15 = 2.98 machine-hours. At 8 productive hours a day that is 0.37 of a day (shown rounded as 0.4 days), and at $95 an hour it costs $283.27. The metric default is simpler: 20 m³ × 0.15 = 3.0 hours, 0.375 of a day, and £135 at £45 an hour. If you think in cubic yards, 0.15 hours per m³ is 0.115 hours per yd³, or about 8.7 yd³ an hour. Got a rate per cubic yard? Divide it by 0.7646 before you enter it, so 0.25 hours per yd³ becomes 0.33 hours per m³.

Allowing for ground, access and weather

The default of 0.15 hours per m³ works out at 6.7 m³ an hour. That's a fair average for a 3-tonne mini-digger in ordinary soil with somewhere close to put the spoil, and it is a planning figure, not a promise. Clay, roots, old foundations and rubble all slow the bucket, and rock may need a breaker. Loading into a dumper or lorry instead of side-casting adds time to every cycle. Tight access, a narrow trench and digging around live services slow things further. For restricted access, a dig beside an occupied house or exposed winter work, add 20 to 30%: 3.0 hours with 25% on top is 3.75 hours.

A better rate comes from the machine itself. You need the bucket size, how full it really comes up and how long one dig, swing, dump and return cycle takes. A 0.08 m³ bucket filling to 80% on a 20-second cycle makes 180 cycles an hour and lifts 11.52 m³ of loose spoil. Allow the usual 50-minute working hour and that drops to 9.6 m³. Ordinary earth bulks up by roughly a quarter once it's dug (clay more, sand less), so measured in the ground it is 9.6 ÷ 1.25 = 7.68 m³ an hour, or 0.13 hours per m³. Time a few real cycles on site and the rate you enter comes from your own job rather than a table.

Hand digging is many times slower than a machine. It also varies so much with the ground and the person doing it that the honest method is to time one metre of trench and scale up. The rate field accepts up to 5 hours per m³ for this.

What this tool does not do

It times the digging and nothing else. Getting the machine on and off site, breaking out concrete or tarmac, trench support, pumping out water, carting spoil away and backfilling are all separate, and on a small job they can take longer than the dig itself. It doesn't work out the volume either. Remember the bulking when you plan spoil removal: 20 m³ taken out of the ground makes about 25 m³ loose to load into skips or lorries.

Nor does it judge whether a dig is safe, whether a trench needs support or whether nearby foundations could be undermined. Those calls belong to a competent person on site and, where foundations or retaining walls are involved, a structural engineer.

On-site considerations for excavation time

Find the buried services before anyone digs. In the US, contact 811 before you dig so the utilities can be marked. In Great Britain, the HSE's HSG47, Avoiding danger from underground services sets out how to plan the work. Other countries run their own dial-before-you-dig services. Waiting for marks, or hand-digging trial holes around a cable, is time the machine rate doesn't include.

Deeper trenches take longer because they need protecting. OSHA's 29 CFR 1926.652 requires a protective system (sloping, benching, shoring or a trench box) for excavations 5 ft (1.52 m) deep or more unless they are entirely in stable rock, and for shallower ones where a competent person sees signs of a possible cave-in. In Great Britain, the HSE's excavation guidance requires a competent person to inspect supports or battering at the start of each shift. Battering the sides back makes the hole bigger and the dig longer, and a trench box costs set-up time every time it moves. Keep people out from under the bucket, and keep spoil and plant back from the edge.

Codes and compliance

Codes rarely say how fast you can dig, but they do govern the hours your crew works and the holes you leave. In the US, federal law requires overtime pay after 40 hours in a workweek for most hourly workers, and some states add daily overtime. In the UK, nobody can be made to work more than 48 hours a week on average unless they opt out, as GOV.UK explains. A programme built on 12-hour digging days usually means overtime rates, tired operators and the mistakes that happen late in a long shift. Digging near a boundary, a public road or a neighbour's foundations can also need permits or notices, depending on where you are, so check with the local authority before you book the machine.

Before you order

Plant hire is often charged by the day or half day rather than by the hour, sometimes with a minimum charge. If yours is, the cost line here understates it. Book a machine and operator for a full 8-hour day at £45 an hour and you pay 8 × £45 = £360, whether the dig takes 3 hours or all 8. Use the working-days figure, round up to whatever the hire company actually charges, and add delivery and collection. Check the machine fits the access (gateway width, overhead cables, ground that will carry it) and that there's room for a dumper or skip if the spoil is leaving site.

Adjusting the defaults

The US side opens at 26 yd³, 0.15 hours per m³, $95 an hour for machine and operator, and an 8-hour day. The metric side opens at 20 m³, 0.15 hours per m³, 45 an hour and 8 hours, shown as £45 in the UK because the currency symbol follows your browser's region. Treat all of them as placeholders. Hire rates in particular vary by country and region, so use a real quote. Set the working day to the hours the machine will actually be digging, after travel, set-up and breaks, not the hours it spends on site.

Using this excavation time calculator alongside other BuildMetricLab tools

Work out the volume first with the excavation volume calculator, then bring it here for the time and cost. If the ground is going back in and being compacted, the soil compaction calculator covers that part. Everything runs in your browser, nothing you type is sent anywhere, and the formula is on the page so you can check each step yourself.